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Bio 101 Exam B

Test: October 21, 2011

Major quality of living things the ability to reproduce
Getting two cells together sexual reproduction, also repairing wounds, or growth from a fertilized egg
Basics grow larger, divide in two
DNA is the key to reproduction, development, and maintenance
Genome complete collection of an organism's genetic information as linked genes in a long strand of DNA
Genes provide just information for the production of Proteins
Proteins perform most of the work of the cell
Information of Genes is found in letters A,C,G, and T in the double helix
Path from DNA to protein DNA -- RNA -- Amino Acid sequence (protein)
Humans have from 20,000 to 25,000genes that have all the information to make all the proteins (especially enzymes) a cell needs
Each descendant of a cell, in addition to requiring nutrients, cell membrane, and organelles, must have this information of DNA to survive
Simple division would mean the new cells had half of what the old cell had
Duplication of both cytoplasmic and nuclear contents precedes division so that new cells have a complete set of everything
Replication Duplication of DNA
DNA is Packaged in chromosomes
Organization of these long pieces of DNA DNA is divided into long strands wrapped around protein (chromatin)
Each DNA strand is packaged and condensed into a single chromosome
Replication takes one Chromosome and makes two identical copies called sister chromatid
Different organisms have different numbers of chromosomes
Eukaryotes have a backup of each chromosome pairs of chromosomes are called homologus chromosomes
Humans have ______ total chromosomes 46, two from each one
Sex chromosomes humans and other mammals use chromosomes to distinguish between the sexes
Male karyotype males have one X and one Y
The cell cycle keeps record of progress of a cell over time, like a clock
The cell cycle is made up of a repeating pattern of growth, genetic duplication, and division
Typical animal cell cycle lasts about 24 hours
Two Main phases of cell cycles interphase and mitotic phase
Interphase G (gave 1) + S phase (synthesis, for replication of DNA) + G2 (Gap 2)
Mitosis how the cell's newly duplicated chromosomes condense, align themselves, and separate.
Interphase duplication of genetic material ends when chromosomes begin to become visible
Prophase the mitotic spindle is forming, emerging from centrosomes
Prophase ends when the chromatim is completely coiled into chromosomes, nucleoli and nuclear membrane disperse
Metaphase the spindle is fully formed; chromosomes are aligned single file with centromeres on the metaphase plate (the plate that cuts the equator)
Each sister chromatid facing opposite poles Metaphase
Anaphase sister chromatids separate; each new chromosomes moves to the opposite pole
Telophase is the reverse of prophase: cell elongation continues, a nuclear envelope forms around chromosomes, chromosomes uncoil, and nucleoli reappear.
Prophase (P for "plain to see") chromosomes condense,nuclear envelope breaks down, spindle fibers (microtubules) are formed from the centrosomes
Metaphase (M for "middle") chromosomes are aligned on the equator but pushing along the spindle with each sister chromatid facing opposite poles
Anaphase (A for "apart") Sister chromatids separate; each new chromosome moves to the opposite pole
Telophase (T for "two nuclei") Chromosomes de-condense, spindle breaks down, nuclear envelope forms around the two separate complements of chromosomes
Cytokinesis how the cell's cytoplasm and membrane separate to create two distinct cells
Cytokinesis begins in anaphase when a waistband- a contractile ring of protein filaments begins to form around the cell
A cleavage furrow forms as the waistband is tightened, eventually completely pinching the cells apart
Plant cells- everything is similar except for cytokinesis because plant cells have to break down and reform the cell wall
Pokaryotes (no nucleus) binary fission
Unrestrained cell division cancer
cancer is a disease of the cell cycle
mechanisms that induce cell division can become hyperactive oncogenes: stuck accelerator
Mechanisms that suppress cell division can fail Tumor suppressor genes: failed brakes
Two types of tumors benign and malignant
Benign tumors abnormal mass of essentially normal cells
Malignant tumors cancerous cells; potential to metasize through the body
Mitosis "Identical" sexual reproduction: combination of desirable traits and more vanability
Problems with Mitosis If combining traits were accomplished just by combining two cells, life would get incredibly complicated. Analogy to couples hyphenating their names when married.
N number of different chromosomes. Adult animals have somatic cells with two sets of homologues
Diploid 2n
Sex cells (gametes= eggs and sperm) have one set of homologues
Homologues are produced by meiosis
Haploid n these cells are made only sexually reproducing organisms and only in a special organ called a gonad (testis and ovary)
seual life cycles involve the alternation between a diploid phase and a haploid phase
The fusion of haploid gametes in the process of fertilization results in the formation of a diploid zygote
Meiosis reduces chromosome number by duplication of chromosomes (S phase) followed by two divisions instead of one (as in mitosis)
Mitosis(a) "Identical" DNA is duplicated; the identical sets (sister chromatids) are divided into 2 cells
Results of Mitosis(a) One diploid cell (2n) becomes two diploid cells (2n)
meiosis "Reductional" each homologue is separated to reduce the total number or chromosomes from a 2n to a n. The the identical sister chromatids are separated
what are the two separate divisions Meiosis I and Meiosis II
Results of Meiosis one diploid cell (2n) becomes four haploid cells, 4 n
Meiosis begins like mitosis does with replication of DNA is S phase of interphase
Meiosis I is when homologues separate
Prophase I 46 identifiable chromosomes (wach with two sister chromatids) are plain to see
homologues chromosomes pair together (tetrad) and crossing over (recombination) occurs
Metaphase I tetrads line up on the metaphase plate
Alignment of one pair bears no relationship to any other pair (paternal chromosome on left, maternal on right)
Anaphase I homologous pairs separate and move to opposite poles
Telephase I at the same time, cytokinesis creates two new cells that are haploid
Meiosis II is when sister chromatids separate
Phrophase II 23 identifiable separate chromosomes (each still with two sister chromatids)
Metaphase II Chromosomes line up at metaphase plate, this time with one sister chromatid on either side
Anaphase II sister chromatids separate
Telophase II two new nuclei form and cytokinesis begins to create two new cells, for a total of four haploid cells
What is the significance of Meiosis first problem problem of chromosome duplication is solved, diversity is created
what is the significance of Meiosis second problem Recombination
Recombination: independent assortment of chromosomes makes sure that no two gametes are ever identical, number of possible combinations= 2N
Humans have 22 pairs of autosomes and one pair of sex chromosomes
females have two x chromosomes
males have one x and one y
sex chromosomes pair like homologous and separate in meiosis I, so each haploid cell that results has either an x or a y in males
sex is determined by the sperm
spermatogenesis spermatogonia, diploid cells that can divide by mitosis to make more of themselves, or make cells destined become sperm called primary spermatocytes
Primary spermatocytes complete meiosis I to give rise to two secondary spermatocytes
secondary spermatocytes complete meiosis II to make four total haploid spermatids
spermatids are mature in about three weeks to form sperm, with flagella tails, concentrated mitochondria and a haploid nucleus
about 250 million sperm are made eacc day, about same number in ejaculate
OOgonia diploid cells that divide by mitosis early in embryogenesis, never divide after birth
most die before birth, but the remaining oogonia make cells destined to become eggs, called primary oocytes
primary oocytes begin meiosis I in the embryo, but do not complete it until ovulation... give rise to one secondary oocyte and a polar body
secondary oocytes complete meiosis II after being fertilized by a sperm, makes one haploid egg
The other products of meiosis are polar bodies
oocyte cytokinesis is unequal to ensure that one large cell, 200,000 times bigger than the sperm, has enough materials to drive early divisions and feed the rapidly dividing embryonic cells
usually only one secondary oocyte is released per 28-day cycle in an adult woman
Dizygotic fraternal twins
monozygotic identical twins
Humans: Meiosis creates haploid gametes that fuse to make a diploid fertilized egg.
The fertilized egg divides trillions of times by mitosis to make a baby
the cells in a human being continue to divide by mitosis to grow and replace cells
Asexual reproduction bacterial fission; single-celled eukaryotes; regeneration; hermaphrodites
Mendel worked in the period from 1856-1863, observing generations of pea plants and applying mathematics to create a set of principles to govern inheritance
without ever knowing what genes were, he figured out how they worked
basic units of genetics are material elements that come in pairs
elements do not change, even over many generations
pairs separate during the formation of gametes
Life cycle allows for rapid generations and cross and self-pollination
wide range of described characters, each of which had two varieties white and purple flower color, yellow and green seed.... - called traits
Phenotype is the physical function, bodily characteristic or action
Genotype is the underlying genes that determine the phenotype
allele alternate for of a gene (trait)
Monohybrid crosses and the segregation of allele
starting generation of test is called P for parental generation; took pollen from one variety and placed it on the stigma of the other variety
Offspring are called F1 for first filial; could have been mix of traits, but they were all yellow (dominant)
To determine where green went, Mendel self-pollinated these F1 plants
Nest generation of offspring is called F2 for second filial (6,022 yello and 2,001 green)
Green came back, but only as a specific proportion- 3:1
Unlike his predecessors, Mendel, carefully counted and interpreted the numbers
Mendel found that varieties did not blend- one is dominant (shows up) and the other recessive (is masked by the dominant)
These varieties are called alleles
The F3: of the yellow F2, two-thirds gave mixtures of green and yellow (not pure yellow parents), and one-third were all yellow in the F3 (pure yellow)
Of the green, all were true breeding. Alleles Y and y
Homozygous vs. Heterozygous how to use a punnet squares to keep track of alleles
Mendel's First Law segregation of alleles: pea cells contain two copies of each gene (alleles)
Alleles do not blend (one copy, dominant, can mask the expression of the recessive copy);
Alleles must separate during Meiosis (Mendel had no knowledge of chromosomes or meiosis): crosses of the F1 and F2 and F3
Genotype determines phenotype: genotpyic and phenotypic ratios
Law of Independent Assortment during gamete formaiton, gene pairs assort independently due to random nature of how tetrads line up during prophase I of meiosis
Genes make proteins red gene makes re pigment; with only one allele, you get only half the pigment
multiple alleles phenotypes and genotypes of all possible combinations of A, B, and O
polygenetic inheritance this situation creates a continuum of phenotypes
identical cuttings of hydrangea macrophylla can be blue or red depending on the soil
take three identical Timberline plants and plant them at different altitudes they will grow to different heights. Same genes, but environment different
Pleiotrophy one gene with multiple effects.
How can sickle cells be both deleterious and protective
Genes code for the proteins that make pigments in the eye necessary for absorbing the different-colored wavelengths in light
red and green pigments are made by genes on the x chromosome
mutations in the genes for these pigments result in inability to see those colors
these mutations are recessive because one good copy of the gene is sufficient for color vision affect men much more frequently than women
because women have two x chromosomes, they can be heterozygous (have one mutant allele) but still have normal color vision (0.5 percent of women are color blind)
Men have only one x chromosome, so if they have one mutant allele, they will be color blind (8 percent are color blind)
Hemophilia is cause by a mutation in a gene that codes for a blood-clotting protein; family tree
sickle-cell anemia, prevalent in populations in or from Africa
Red Blood cells become distorted into sickle shape in low oxygen
Mutation is in the gene for the B-chain protein of hemoglobin
Hemoglobin S has a substitution of one amino acid, causing the chain to coalesce into crystals that distort the red blood cells
Persons with one S allele and one normal A allele do not have the condition, but are called carriers because they can pass the gene on to their offspring (8 percent of African Americans are cariers).
One in 12 African-American children in the U.S. has sickle cell anemia
Cystic Fibrosis most common genetic disorder in Caucasian Americans; 1 in 25 is a carrier. Primarily affects the body's respiratory and digestive systems. It is due to a gene defect that causes the body to produce abnormally thick mucous.
Tay-Sachs most common in Jewish Americans of Central European descent; 1 in 25 a carrier.
Babies with Tay-Sachs lack an enzyme (protein) necessary for breaking down certain fatty substances in brain and nerve cells. These substances build up and gradually destroy brain and nerve cells, until the entire central nervous system stops working.
Both parents must have the allele to have a child born with the condition
even in both parents are carriers, they have one-in-four chance of having an offspring with the condition
In the case of sickle-cell anemia, which occurs more frequently in populations from malaria-ravaged sections of Africa, heterozygotes are more resistant to malarial infection
Malaria is caused by a protozoan parasite
Only one copy of the allele is sufficient for the child to express the condition
Patterns of inheritance single "faulty" allele of a gene cause damage, even with a "good" allele present
Confronted with medical condition running in a family, geneticists like to create family tree diagrams or pedigrees, which can be used to determine if the disorder is dominant or recessive, and the probability of future inheritance
What is the relationship between DNA and proteins? DNA encodes for proteins, and protein enzymes replicate and maintain DNA
Error rate minimized by DNA polymerase proof reading
DNA encodes for proteins, and protein enzymes replicate and maintain DNA
Mutation permanent alteration in cell's DNA base sequence
Point mutations slight change in chemical form of base, or incorrect base pairs
Almost all cancers begin as a mutation that is passed along at replication (somatic cells). Mutation rate is low, but after decades of accumulated mutations, cells can become malignant
Heritable mutations occur in germ-line cells (cells that divide to make sperm and eggs)
What is the benefit of mutations? They create new alleles of genes
Polypeptides (proteins) are large organic macromolecules made up of strands of hundreds or thousands of amino acids joined together by peptide bonds
There are only 20 different amino acids they can be recombined in thousands of ways
How does a specific strand of amino acids always come to be strung together in the same order? DNA (a strand of nucleotide letters, A,C,G, and T) is read as a code. Code translated into amino acids sequence. Every protein has the identical amino acids in order along its length.
Protein Synthesis: First Stage DNA resides in the nucleus, but proteins are made in the cytoplasm
DNA is the mast set of instructions for the cell, so it needs to stay protected and isolated in the nucleus
Instead of allowing DNA to leave the nucleus and travel to the cytoplasm the cell makes a cheap copy of DNA in a smaller less permanent form
The process of copying DNA into RNA copy is called transcription
the correct amino acid is added at the correct time by using the information on the RNA message from the nucleus
Process of assembling proteins from RNA instructions is called translation
the units of both RNA and DNA are composed of sugars, phosphates and bases
Sugars are different in RNA and DNA Ribose in RNA and Deoxyribose in DNA
RNA has nitrogen-containing bases A,G,C, and U instead of T
mRNA Messenger RNA carries instructions for sequence of amino acids in a protein
rRNA ribosomal RNA is an important component of ribosomes
tRNA transfer RNA is involved in matching the correct amino acid to specific instructions in mRNA
Just like replication base pairing is the mechanism used to copy DNA in transcription, but here into RNA and not DNA
Enzyme critical to catalyzing this process is RNA Polymerase
DNA is unwound and used as a template to match complementary bases, C to G and A to U (not T) to make a new daughter strand
The new nucleotides are covalently linked together by the same enzyme to make a single strand of RNA (called a transcript t) from one strand of the double helix
Four bases in DNA, 20 amino acids in protein not one to one or two to one: a triplet code-three nucleotides (called a codon) signifying one amino acid
There are 64 different possible combinations of the four nucleotides, more than enough for the 20 different amino acids
The code is redundant (several different codons signify the same amino acid)
The Code carries instruction codons for stopping and starting
The genetic code is universal (same for bacteria and humans) and is good evidence for a common inheritance (evolution)
mRNA carries the instructions in the codons, like a recipe
Ribosomes, location of protein synthesis, are a large conglomerate of enzymes and ribosomal RNA (rRNA) in two subunits with A and P sites
tRNA molecules (transfer RNA) are "translator" molecules; they can match the appropriate amino acid with the codon in the mRNA.
Part of the molecule binds an amino acid, and the other end has three nucleotides (anticodon) that form a base pair with the codon in the mRNA
mRNA binds to the small subunit of the ribosome
Start codon, AUG, brings in initiator tRNA with the amino acid methionine, and then large subunit binds
tRNA that matches the next codon ferries in the appropriate amino acid into the "A" site
The ribosome catalyzes the peptide bond between the first two amino acids at the "A" site; then the ribosome jumps along the mRNA to the next codon, moving the newly formed peptide to the "P" site
At the stop codon, no new tRNA comes into the "A" site, and the whole complex falls apart, releasing the new protein
Five amino acids are added every second, and multiple ribosomes move along a transcript simultaneously
What is a gene a segment of DNA that makes transcript
Created by: kslack1080
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