Question 1

deoxyribonucleic acid (DNA)

Accepted Answer

a double-stranded nucleic acid
chain made up of nucleotides.
DNA carries the instructions for
proteins which are required for
cell and organism survival

Question 2

where does DNA sit

Accepted Answer

sits inside the nucleus of your cells and is formed
by the continuous pairing of base pairs into a longer, double-stranded nucleic acid chain

Question 3

nucleic acid

Accepted Answer

the class of
macromolecules that includes
DNA and RNA. All nucleic
acids are polymers made out of
nucleotide monomers

Question 4

nucleotide

Accepted Answer

the monomer unit
of nucleic acids. Made up of
a nitrogen-containing base, a
sugar molecule (ribose in RNA
and deoxyribose in DNA), and a
phosphate group

Question 5

nitrogen containing base include:

Accepted Answer

-adenine (A)
− thymine (T)
− guanine (G)
− cytosine (C)

Question 6

gene

Accepted Answer

a section of DNA that
carries the code to make a protein, acts like a set of instructions which a cell will then read to create the
important protein molecules needed for a range of cellular functions, such as growth and
regeneration.

Question 7

order of bases

Accepted Answer

The order of bases in the double helix determines which protein gets made.
For instance, the sequence ‘ATG’ will send different instructions than the sequence ‘GGG’

Question 8

how many copies of each gene does individuals have

Accepted Answer

Each person has two copies of each gene, one inherited from their mother and the other
from their father. In total, there are roughly 25 000 different genes inside each of your
cells. We call this collection of genes your genome

Question 9

genome

Accepted Answer

the complete set of
DNA contained within an
organism’s chromosomes, houses all of the genetic
information needed to build and maintain you: a complex organism.

Question 10

allele

Accepted Answer

alternate forms of a gene, are different forms of the same gene but with small differences in
their base sequence.

Question 11

alleles compared to genes

Accepted Answer

Almost all genes are the same across every human being. However, a small number
of genes are slightly different between people, which contributes to the
immense differences we see from person to person. These differences are a result of alleles,

Question 12

example

Accepted Answer

we each have genes that are responsible for the colour of our eyes. differences are
caused by differences in the alleles you each possess for the genes involved with eye
colour

Question 13

gene locus

Accepted Answer

the fixed position
on a chromosome where a
particular gene is located

Question 14

how many alleles are present at the gene locus

Accepted Answer

only two alleles are present at the gene locus of any one individual, each of
which is inherited from one parent – one from mum and one from dad. The allele that is
ultimately expressed in your phenotype

Question 15

phenotype

Accepted Answer

the observable trait of
an individual

Question 16

how is a genome measured

Accepted Answer

by the number
of base pairs contained in a haploid set of chromosomes. For example, the human genome
is around three billion base pairs in length (haploid), which equates to roughly 25 000
different genes

Question 17

where does the genome sit

Accepted Answer

sits inside the nucleus of each of their somatic cells in the form
of DNA, which is then wrapped around proteins to form chromosomes.

Question 18

how are chromosomes arranged

Accepted Answer

arranged into homologous pairs based on the specific genes they possess.

Question 19

chromosomes

Accepted Answer

each molecule of DNA is coiled tightly around histone proteins and packaged
into thread-like structures called chromosomes. Human somatic cells mostly contain
46 chromosomes and therefore have a diploid number of 2n = 46.

Question 20

histone protein

Accepted Answer

highly basic
proteins that associate with DNA
inside the nucleus and help it
condense into a chromosome
allowing it to fit inside the nucleus

Question 21

chromosome size

Accepted Answer

vary in size depending
on the number of nucleotides they contain. Each individual gene
has its own gene locus on the chromosome

Question 22

features of a chromosome

Accepted Answer

telomeres (A region of repetitive base sequences that is found at the end of every chromosome), DNA molecule (colied around HP)  centromere(A specialised sequence of DNA that holds together the two chromatids), sister chromatids, short arm and long arm

Question 23

Centromerehomologous chromosomes

Accepted Answer

a
pair of chromosomes of similar
length, gene position, and
centromere location. One of the
pair is inherited from the mother
(maternal chromosome) and
the other from the father
(paternal chromosome)

Question 24

The criteria for homologous chromosomes are

Accepted Answer

1 they are the same in size and length
2 they have the same centromere position
3 they share the same genes at the same gene loci.

Question 25

do they have to be identical in base sequence?

Accepted Answer

while not identical in base sequence, are paired and identified
together as they contain the same genes, and must have teh same loci

Question 26

karyotype

Accepted Answer

a visual representation
of an individual’s entire genome
organised into homologous pairs, a shared
structural features and is used to check for possible genetic abnormalities.

Question 27

autosome

Accepted Answer

any chromosome
(1–22) in humans that is not
a sex chromosome

Question 28

sex chromosome

Accepted Answer

a chromosome
responsible for determining the
biological sex of an organism.
In humans, sex chromosomes can
be either an X or Y chromosome

Question 29

aneuploidy

Accepted Answer

when a cell or
organism varies in the usual
number of chromosomes in its
genome by the addition or loss
of a chromosome

Question 30

polyploidy

Accepted Answer

when an organism
contains additional sets of
chromosomes in its genome (3n=72)

Question 31

monosomy.

Accepted Answer

a genetic abnormality
where an organism has one
missing chromosome

Question 32

trisomy

Accepted Answer

a genetic abnormality
where an organism has one
extra chromosome

Question 33

tetrasomy.

Accepted Answer

a genetic abnormality
where an organism has two
extra chromosomes

Question 34

meiosis

Accepted Answer

a specialised form of cell
division used to produce gametes
in sexually reproducing organisms 
and  is used to produce the gametes necessary for sexual reproduction

Question 35

gametes

Accepted Answer

reproductive cells that
arise from germline cells and
contain half the genetic material
(n) of a somatic cell. The gametes
in animals are sperm and egg cells

Question 36

zygote

Accepted Answer

the diploid cell formed by
the combination of two haploid
gamete cells

Question 37

two types of cellular division

Accepted Answer

meiosis I – which separates each homologous chromosome into two different cells.
• meiosis II – which separates each sister chromatid into four different cells.

Question 38

before division

Accepted Answer

Homologous pair of chromosomes, one diploid, one parent cell (2n, 2s)

Question 39

Interphase

Accepted Answer

Homologous pair of replicated chromosomes, (2n, 4s)

Question 40

Meiosis I

Accepted Answer

Each homologous chromosome is
separated into a dierent haploid cell (n, 2s)

Question 41

Meiosis II — second cell division

Accepted Answer

Each sister chromatid is
separated into one of four
haploid cells, four haploid daughter cells (n, s)

Question 42

mitosis

Accepted Answer

used by almost every cell in your body and results in the production of two identical copies
of the original cell, important development and growth and is also
used to replace old or malfunctioning cells within our body with identical copies.

Question 43

meiois purpose

Accepted Answer

to produce gametes which
have exactly half the genetic material of the original cell. This is important for sexual
reproduction so that when two gametes fuse during fertilisation, the resulting offspring
does not inherit double

Question 44

mitosis vs meiosis

Accepted Answer

MIT: input (1 somatic cell (2n)- output (2 identical somatic  cells 2n)
MEIS: input(1 germline cell 2n)-output(4 geneticallly unique gamete cells n)

Question 45

Interphase M1

Accepted Answer

Before meiosis, a cell must go through interphase. This stage is
identical to that of mitosis, where the cell grows and duplicates
all of its chromosomes in preparation for division.

Question 46

Prophase I

Accepted Answer

The nuclear membrane breaks down as chromosomes condense
and line up in homologous pairs. This is important for crossing
over of genetic material between the homologues

Question 47

Metaphase I

Accepted Answer

Homologous chromosomes will then line up randomly on
opposite sides of the metaphase plate, with one paternal
or maternal, Each chromosome is attached to microtubules of whichever pole it is closest to

Question 48

Anaphase I

Accepted Answer

The homologous chromosomes are moved apart towards
opposite poles of the cell. However, for now, sister chromatids
remain attached to one another at the centromere.

Question 49

Telophase I

Accepted Answer

The chromosomes arrive at opposite ends of the cell as the
nuclear membrane is cleaved. A cleavage furrow forms in
preparation for the cell to undergo cytokinesis.

Question 50

how does genetic variation occur

Accepted Answer

crossing over and independent assortment

Question 51

crossing over

Accepted Answer

the exchane of genetic material between non sister chronatids during prophase 1 of meiosis, resulting in new combinations of allels in daughter cells

Question 52

independent assortment

Accepted Answer

the random orietation of homologous chromosomes along the metaphase plaste during metaphase 1

Question 53

where does crossing over occur

Accepted Answer

the point called the chiasma where the two non siter chromatids overlap

Question 54

Why is this important for genetic diversity: CO

Accepted Answer

CO results in teh formation of new recombiannt chromatids each with its own unique combination of alleles, adds to gentic diversity of teh resulting haploid daughter cell as teh sister chromatids they they inherit are no longer identical

Question 55

Why is this important for genetic diversity: IA

Accepted Answer

teh reuslting combination of alleles in each daughter cell is randomized since what is inherited depends on whoch side of the metaphase plate each chromosome is positioned

Question 56

Prophase II

Accepted Answer

the nuclear
envelope begins to break down, the chromosomes condense,
and the spindle fibres form in preparation to pull apart the
sister chromatids of each chromosome.

Question 57

Metaphase II

Accepted Answer

Each chromosome lines up along the metaphase plate of the
cell, as microtubules from opposite poles of the cell prepare
to pull the chromosomes apart.

Question 58

Anaphase II

Accepted Answer

Sister chromatids are now separated and pulled towards
opposite poles of the cell by microtubules, which are
attached at each centromere.

Question 59

Telophase II

Accepted Answer

With individual chromatids now at each pole of the cell,
separate nuclear membranes begin to form around each
set as the chromosomes begin to decondense and unravel.

Question 60

Cytokinesis

Accepted Answer

Cytokinesis splits each of the chromosome sets at opposite
ends of the cell into four new, individual cells. The resulting
daughter cells are haploid.

Question 61

how are traits controlled

Accepted Answer

controlled
by a number of genes, each of which produces individual proteins that will interact with
one another and contribute to the overall physical phenotype of the organism.

Question 62

phenotype is due to

Accepted Answer

genetic material and its environmnet

Question 63

proportionate heritability

Accepted Answer

the amount of phenotypic variance
that can be explained by genes
in a given population, tells us that an organisms phenotype can be entirely due to the environment

Question 64

do environmental factors effect gene expression

Accepted Answer

will rarely affect
levels of gene expression itself,  environmental factors will typically act in ways that influence the performance
of an organism’s proteins in their phenotype, modifies the function of proeins, rather than affecting teh creation

Biology Chapter 7

7A, 7B, 7C, 7D

Question	Answer
deoxyribonucleic acid (DNA)	a double-stranded nucleic acid chain made up of nucleotides. DNA carries the instructions for proteins which are required for cell and organism survival
where does DNA sit	sits inside the nucleus of your cells and is formed by the continuous pairing of base pairs into a longer, double-stranded nucleic acid chain
nucleic acid	the class of macromolecules that includes DNA and RNA. All nucleic acids are polymers made out of nucleotide monomers
nucleotide	the monomer unit of nucleic acids. Made up of a nitrogen-containing base, a sugar molecule (ribose in RNA and deoxyribose in DNA), and a phosphate group
nitrogen containing base include:	-adenine (A) − thymine (T) − guanine (G) − cytosine (C)
gene	a section of DNA that carries the code to make a protein, acts like a set of instructions which a cell will then read to create the important protein molecules needed for a range of cellular functions, such as growth and regeneration.
order of bases	The order of bases in the double helix determines which protein gets made. For instance, the sequence ‘ATG’ will send different instructions than the sequence ‘GGG’
how many copies of each gene does individuals have	Each person has two copies of each gene, one inherited from their mother and the other from their father. In total, there are roughly 25 000 different genes inside each of your cells. We call this collection of genes your genome
genome	the complete set of DNA contained within an organism’s chromosomes, houses all of the genetic information needed to build and maintain you: a complex organism.
allele	alternate forms of a gene, are different forms of the same gene but with small differences in their base sequence.
alleles compared to genes	Almost all genes are the same across every human being. However, a small number of genes are slightly different between people, which contributes to the immense differences we see from person to person. These differences are a result of alleles,
example	we each have genes that are responsible for the colour of our eyes. differences are caused by differences in the alleles you each possess for the genes involved with eye colour
gene locus	the fixed position on a chromosome where a particular gene is located
how many alleles are present at the gene locus	only two alleles are present at the gene locus of any one individual, each of which is inherited from one parent – one from mum and one from dad. The allele that is ultimately expressed in your phenotype
phenotype	the observable trait of an individual
how is a genome measured	by the number of base pairs contained in a haploid set of chromosomes. For example, the human genome is around three billion base pairs in length (haploid), which equates to roughly 25 000 different genes
where does the genome sit	sits inside the nucleus of each of their somatic cells in the form of DNA, which is then wrapped around proteins to form chromosomes.
how are chromosomes arranged	arranged into homologous pairs based on the specific genes they possess.
chromosomes	each molecule of DNA is coiled tightly around histone proteins and packaged into thread-like structures called chromosomes. Human somatic cells mostly contain 46 chromosomes and therefore have a diploid number of 2n = 46.
histone protein	highly basic proteins that associate with DNA inside the nucleus and help it condense into a chromosome allowing it to fit inside the nucleus
chromosome size	vary in size depending on the number of nucleotides they contain. Each individual gene has its own gene locus on the chromosome
features of a chromosome	telomeres (A region of repetitive base sequences that is found at the end of every chromosome), DNA molecule (colied around HP) centromere(A specialised sequence of DNA that holds together the two chromatids), sister chromatids, short arm and long arm
Centromerehomologous chromosomes	a pair of chromosomes of similar length, gene position, and centromere location. One of the pair is inherited from the mother (maternal chromosome) and the other from the father (paternal chromosome)
The criteria for homologous chromosomes are	1 they are the same in size and length 2 they have the same centromere position 3 they share the same genes at the same gene loci.
do they have to be identical in base sequence?	while not identical in base sequence, are paired and identified together as they contain the same genes, and must have teh same loci
karyotype	a visual representation of an individual’s entire genome organised into homologous pairs, a shared structural features and is used to check for possible genetic abnormalities.
autosome	any chromosome (1–22) in humans that is not a sex chromosome
sex chromosome	a chromosome responsible for determining the biological sex of an organism. In humans, sex chromosomes can be either an X or Y chromosome
aneuploidy	when a cell or organism varies in the usual number of chromosomes in its genome by the addition or loss of a chromosome
polyploidy	when an organism contains additional sets of chromosomes in its genome (3n=72)
monosomy.	a genetic abnormality where an organism has one missing chromosome
trisomy	a genetic abnormality where an organism has one extra chromosome
tetrasomy.	a genetic abnormality where an organism has two extra chromosomes
meiosis	a specialised form of cell division used to produce gametes in sexually reproducing organisms and is used to produce the gametes necessary for sexual reproduction
gametes	reproductive cells that arise from germline cells and contain half the genetic material (n) of a somatic cell. The gametes in animals are sperm and egg cells
zygote	the diploid cell formed by the combination of two haploid gamete cells
two types of cellular division	meiosis I – which separates each homologous chromosome into two different cells. • meiosis II – which separates each sister chromatid into four different cells.
before division	Homologous pair of chromosomes, one diploid, one parent cell (2n, 2s)
Interphase	Homologous pair of replicated chromosomes, (2n, 4s)
Meiosis I	Each homologous chromosome is separated into a dierent haploid cell (n, 2s)
Meiosis II — second cell division	Each sister chromatid is separated into one of four haploid cells, four haploid daughter cells (n, s)
mitosis	used by almost every cell in your body and results in the production of two identical copies of the original cell, important development and growth and is also used to replace old or malfunctioning cells within our body with identical copies.
meiois purpose	to produce gametes which have exactly half the genetic material of the original cell. This is important for sexual reproduction so that when two gametes fuse during fertilisation, the resulting offspring does not inherit double
mitosis vs meiosis	MIT: input (1 somatic cell (2n)- output (2 identical somatic cells 2n) MEIS: input(1 germline cell 2n)-output(4 geneticallly unique gamete cells n)
Interphase M1	Before meiosis, a cell must go through interphase. This stage is identical to that of mitosis, where the cell grows and duplicates all of its chromosomes in preparation for division.
Prophase I	The nuclear membrane breaks down as chromosomes condense and line up in homologous pairs. This is important for crossing over of genetic material between the homologues
Metaphase I	Homologous chromosomes will then line up randomly on opposite sides of the metaphase plate, with one paternal or maternal, Each chromosome is attached to microtubules of whichever pole it is closest to
Anaphase I	The homologous chromosomes are moved apart towards opposite poles of the cell. However, for now, sister chromatids remain attached to one another at the centromere.
Telophase I	The chromosomes arrive at opposite ends of the cell as the nuclear membrane is cleaved. A cleavage furrow forms in preparation for the cell to undergo cytokinesis.
how does genetic variation occur	crossing over and independent assortment
crossing over	the exchane of genetic material between non sister chronatids during prophase 1 of meiosis, resulting in new combinations of allels in daughter cells
independent assortment	the random orietation of homologous chromosomes along the metaphase plaste during metaphase 1
where does crossing over occur	the point called the chiasma where the two non siter chromatids overlap
Why is this important for genetic diversity: CO	CO results in teh formation of new recombiannt chromatids each with its own unique combination of alleles, adds to gentic diversity of teh resulting haploid daughter cell as teh sister chromatids they they inherit are no longer identical
Why is this important for genetic diversity: IA	teh reuslting combination of alleles in each daughter cell is randomized since what is inherited depends on whoch side of the metaphase plate each chromosome is positioned
Prophase II	the nuclear envelope begins to break down, the chromosomes condense, and the spindle fibres form in preparation to pull apart the sister chromatids of each chromosome.
Metaphase II	Each chromosome lines up along the metaphase plate of the cell, as microtubules from opposite poles of the cell prepare to pull the chromosomes apart.
Anaphase II	Sister chromatids are now separated and pulled towards opposite poles of the cell by microtubules, which are attached at each centromere.
Telophase II	With individual chromatids now at each pole of the cell, separate nuclear membranes begin to form around each set as the chromosomes begin to decondense and unravel.
Cytokinesis	Cytokinesis splits each of the chromosome sets at opposite ends of the cell into four new, individual cells. The resulting daughter cells are haploid.
how are traits controlled	controlled by a number of genes, each of which produces individual proteins that will interact with one another and contribute to the overall physical phenotype of the organism.
phenotype is due to	genetic material and its environmnet
proportionate heritability	the amount of phenotypic variance that can be explained by genes in a given population, tells us that an organisms phenotype can be entirely due to the environment
do environmental factors effect gene expression	will rarely affect levels of gene expression itself, environmental factors will typically act in ways that influence the performance of an organism’s proteins in their phenotype, modifies the function of proeins, rather than affecting teh creation
epigenetics	changes to an organism’s phenotype resulting from modifications to gene expression
epigentci modifications	In some cases environmental factors may cause changes to a gene that activate or deactivate the expression of that gene, affects the amount of protein produced, which subsequently alters an individual’s phenotype, bridge between enviroment and genotype
how does epigenetic modifications work	Environmental signals are translated into biochemical changes inside a cell that lead to increased or decreased gene expression.
hw does it affect gene exression	epigenetic factors influence gene expression by determining which genes are ‘turned on or off’, but they do not alter the actual DNA sequence. This is often in response to environmental changes, such as exposure to certain chemical
gene expression	the process of reading the information stored within a gene to create a functional product, typically a protein
How does epigenetics work?	A gene is expressed when the protein it carries the instructions for is built by a cell. This occurs through the processes of transcription and translation
transcription	he process whereby a sequence of DNA is used to produce a complementary sequence of mRNA
transcription process	reading and copying out a gene sequence from a DNA molecule. This ‘copy’ of the gene (called mRNA) then moves out of the nucleus to ribosomes in the cytosol or on the rough endoplasmic reticulum for translation.
translation	the process whereby an mRNA sequence is used to produce a protein
translation process	mRNA instructs the ribosome how to build the specific protein for which the DNA sequence codes, resulting in a protein
what does epigenetic changes alter	the process of transcription, caused by molecules that increase or decrease the amount of transcription of a particular gene and alter the amount of protein that is produced( regulate the expression of specific proteins).
eg	epigenetic factor of X present-> gene Z turned on-> protein produced-> phenotype A epigentic factor X absent-> gene Z turned off->no protein produced-> phenotype B
Two types of epigenetic changes that	Dna methylation, histone modification
DNA methylation	the process by which methyl (-CH3 ) groups are added to particular nucleotides in a DNA segment so as to repress the expression of a gene
DNA methylation process	when methyl groups attach to certain nucleotides within the DNA sequence of a particular gene and alter levels of gene expression (normally silences it) DNA demethylation removed CH3, expressed it
histone modification	occurs when histone-modifying enzymes known as histone methyltransferases (HMT) join methyl groups to histone tails and modify how tightly a DNA molecule is wrapped around it.
how does histone modification effect gene expression	If DNA is condensed tighter around the histone, it makes it more difficult for the genes to be transcribed and less likely to be expressed. if DNA becomes less tightly packed, the genes will be easier to transcribe and more likely to be expressed.
importance of epigenetics	helps control cell differntition -the developemnt of differnces is regulated by epigentic mechanisms, proved a mechanism for a developing organism to respond to ist environment- acts as rapid feedback so it can respond to changes in tehir enviornment
epigenetics across generations	epigenetic changes can be passed onto daughter cells during mitosis, could affect an individual organism through their whole life therefore somatically heritbale, erased when gametes are formed as not alteratiosn to genome) but some can still be passed on
somatically heritable	genetic traits or alterations to a cell which are inherited by daughter cells during teh course of regular mitotic cell division
diploid organism	inherits a particular combination of two alleles from their parents. If an individual inherits two identical alleles from both their mother and father
homozygous	having identical alleles for the same gene on homologous chromosomes
heterozygous	having different alleles for the same gene on homologous chromosomes
dominant allele	the variant of a gene that masks the effect of a recessive allele of the same gene on a homologous chromosome
recessive allele	the variant of a gene that is masked by a dominant allele on a homologous chromosome
complete dominance	a pattern of dominance where only the dominant allele from the genotype of a heterozygous individual is expressed in the phenotype of that organism
carrier	an organism that has inherited a copy of a recessive allele for a genetic trait but does not display the trait due to it being masked by the presence of a dominant allele
HETEROZYGOTE ADVANTAGE	carrying a typically disadvantageous allele can create an overall biological advantage for the organism, explaisn why harmful recessive alleles are able to persist in a population, hidden in fit heterozygotes, rather than natural sellection removal
genotype	the genetic composition of an organism at one particular gene locus, as represented using letter symbols
codominance	a pattern of dominance where both alleles from the genotype of a heterozygous individual are dominant and expressed in the phenotype of that organism, both alleles are dominant (red+white)
incomplete dominance	a pattern of dominance where neither allele from the genotype of a heterozygous individual is dominant and both are expressed in an intermediate phenotype (pink)
sex-linked genes	genes that are located on a sex chromosome , present on either the X or Y chromosomes
X-linked traits	a trait controlled by a gene that is located on the X chromosome
Y-linked traits	a trait controlled by a gene that is located on the Y chromosome (rare and only show up in males)
X linked traits patterns	more likely to be expressed in males as each male only receives one copy of an X chromosome, whatever allele a male receives on the inherited copy of their X chromosome is what is expressed in their phenotype, regardless dominant or recessive.
can males pass on their X linked traits to their son	are unable to pass the trait on to their sons. This is because if a male has a son, that son must receive their Y chromosome from their father. Affected males can only pass on the abnormal X-linked gene to their daughters
Sex-linked genotypes	are written differently, following a similar superscript notation as codominance and incomplete dominance. However, the standard base letter is always X or Y.
Nondisjunction	in meiosis is when chromosomes fail to separate properly during cell division. This error leads to gametes (eggs or sperm) with an incorrect number of chromosomes, which can cause genetic disorders like Down syndrome.

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