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Exam 2 Genetics

Chapters 6-10

Visual representation of family tree with history of studied trait. Pedigree
Oldest generation at the____; youngest generation at the _____. Top; Bottom
Used for generations (I being the oldest). Roman numerals
Numbered from _____ to _____ within a single generation Left; Right
Trait seen in roughly equal amounts of males and females Seem to skip generations. (Affected individual can have unaffected parents). Autosomal recessive traits
Equal frequency of males and females No skipping of generations All affected individuals have an affected parent (affected individuals tend to be heterozygous) Autosomal dominant traits
Affected phenotype seen more commonly in males Tend to skip generations. Affected males do not pass trait to sons. If woman is affected, 100% of sons will be affected X linked recessive
Do not skip generations Seen in both males and females but more in females. Females can get disease from either parent while males can only get from mother Affected female will have 100% sons affected. Affected male will have 100% daughters affected X linked dominant
Only males affected Affected males will have 100% affected sons Do not skip generations Y linked
Non-identical twins; fraternal 2 separate eggs fertilized 50% average relatedness; same as any sibling pair Dizygotic
Identical One zygote that splits very early in embryonic development Monozygotic
% of twin pairs that have the same trait Monozygotic twins are 100% genetically identical; dizygotic approx 50% Used to evaluate genetic vs environmental factors Genetic influenced traits will show higher concordance in monozygotic twins Concordance studies
Examines effects of genes vs environment Adoption parents have 0% relatedness to adopted child, but share same environment Adoptees tend to resemble biological parents (obesity, alcoholism) Adoption studies
bacteria acquired genetic information from dead strain which permanently changed bacteria Transformation (Fred Griffith)
What are the reasons for seeing a genetic counselor? Positive family history Advanced maternal age Abnormal prenatal test results Infertility Ethnic background
What are some prenatal testing Ultrasound, Amniocentesis, Chorionic villi sampling (CVS), Fetal cell sorting, Pre-implantation
What is a Postnatal testing? Newborn screening, Heterozygote/carrier testing, Pre-symptomatic testing, Chromosome analysis/cytogenetic testing.
What's an Ultrasound? Can be performed as early as several weeks after fertilization Noninvasive Gives image of fetus Anatomical abnormalities, neural tube defects, nuchal translucency, amount of amniotic fluid, fetal size
What is a Amniocentesis? Can be done 15-18 weeks Trans-abdominally or trans-vaginally Ultrasound guided Needle inserted and ~15ml of fluid extracted Fluid can be tested directly or fetal cells cultured prior to testing. Each ml of fluid contains only ~10-15 cells
What's a Chorionic villi sampling (CVS) Ultrasound guided Small section of chorion is suctioned off (10-15mg) Large number of fetal cells reduces time/need for culturing Increased risk for limb reduction of performed at earlier gestation Eliminates proper blood supply to developing li
Isolation of fetal cells from maternal bloodstream Minimally invasive Fetal cell sorting (in development)
IVF procedure One cell is removed from 8-16 cell embryo and tested Only “healthy” embryos are implanted Pre-implantation
Positive family history or particular ethnic background Biochemical or molecular testing Heterozygote/carrier testing
Inherited cancer alleles – increased risk for cancer Late-onset diseases (Huntington disease) Pre-symptomatic testing
Diagnostic and prognostic value in cancer Infertility Child with structural chromosomal abnormality (Inherited or de novo mutation) Chromosome analysis/cytogenetic testing
Diploid organisms have 2 alleles for each gene that Separate during meiosis – only one gamete enters each gamete Principle of Segregation
DNA made up of 4 different nucleotides in equal amounts Tetranucleotide theory
2 alleles of a gene separate independently from alleles at other loci/other genes Principle of Independent Assortment
Chromosomes follow independent assortment if…. genes are on the same chromosome, they tend to travel together
close together on the same chromosome Linked genes
If 2 genes are on the same chromosome, but far apart, crossing over can allow for recombination of gametes crossing over
Genes very far apart on the same chromosome will always be separated by_____, and are not considered to be ___. crossing over; linked
Horizontal lines indicate Actual chromosome
individual heterozygous for 2 different genes where both dominant alleles are on __________, and both recessive alleles are on its _________. One chromosome; homologous chromosome
For determination if two genes are linked and genotype is known. Testcross
One individual heterozygous for both traits x individual homozygous recessive for both traits Testcross setup for linkage
If not closely linked, alleles will assort ______. independently
2 alleles will always travel together, All offspring are non-recombinant If closely linked
If closely linked, it can be separated by crossing over
Small number of recombinant progeny/chromosomes is seen when Crossing over
Single cross over produces 50% _______ and 50% Nonrecombinant chromosomes; recombinant chromosomes
= number of recombinant progeny x 100 total number of progeny Recombination frequency
Smaller the recombination frequency More closely linked
Genes are linked 50%
Genes are not linked <50%
Both wildtype alleles are on one chromosome; both mutant alleles are on the homologous chromosome Cis configuration/coupling
Each chromosome has one wildtype allele and one mutant allele Trans configuration/repulsion
Coupling and Repulsion for ________ individuals heterozygous
Between genes on different chromosomes Independent assortment/random segregation during Metaphase/Anaphase I Produces 50% recombinant/50% non-recombinant gametes Interchromosomal
Between genes on same chromosome Crossing over during Prophase I Usually produces recombinant gametes less than 50% Intrachromosomal
Relative position of different genes based on recombination rates Does NOT state actual chromosome, or position (locus) Distance measured in map units or centimorgans (cM) Genetic mapping
Any genes with 50% recombination are either__________, or very far apart on the ________. (crossing over always separates them) on different chromosomes; same chromosome
Locates gene to a specific chromosome/region of chromosome Physical mapping
Chromosome deletion studies – how phenotype is affected/what genes may be missing Deletion mapping
Fusion of 2 cell types (altered by viruses or tumor cells to allow cell lines – uninhibited growth) Most chromosomes are lost Somatic cell hybridization
2 distinct nuclei Heterokaryon
Fluorescence In Situ Hybridization and DNA sequencing Molecular Analysis
Yields base pair distance between two genes DNA sequencing
Probe complementary to gene sequence will bind to DNA Fluorescence In Situ Hybridization (FISH)
Example of deletion mapping Duchenne m.s. -Some affected males have small deletions -X linked disease (common area for all of them)
Types of Bacteria Prototrophic and Auxotrophic
Wild-type Can grow on minimal media Contains minimal nutrients – carbon, nitrogen, phosphorous, vitamins, ions Prototrophic
Can not produce an essential enzyme or manufacture essential molecules Will only grow on media that contains the “missing” substance Complete media Auxotrophic
Liquid media Bacteria dies off when nutrients are used up or waste buildup becomes toxic Bacteria grow singularly – no colonies Suspension culture
Growth media in agar Isolate individual colonies Each colony originates from a single bacterium Culturing bacteria on Petri dishes
Gives “carbon copies” of petri dish colonies Use sterilized velvet to make a stamp Some bacteria from each colony is transferred to velvet, and then transferred to new dishes Replica plating
Most consist of a single, circular chromosome Very little “extra” DNA between genes Plasmids Bacterial genome
A plasmid that can replicate independently AND also has the ability to incorporate into chromosomes F factor episome
One bacteria directly transfers DNA to another bacterium Cytoplasmic connection forms, and either entire plasmid or part of the chromosome is transferred from donor to recipient Crossing over may occur between homolgous regions Conjugation
Bacteria takes up DNA from surrounding environment Recombination may occur Transformation
Viral particle introduced DNA from a bacterium into a new bacterium Transduction
Fertility factor/F factor contains ori and genes needed for? conjugation
Forms a sex pilus – extension of cell membrane __ factor separates, and one strand is transferred into ___ __ contains __ factor F; F- F+; F
F+ cell that has F factor incorporated into chromosome HFr bacteria
As F factor enters recipient, some chromsome enters – amount depends on time length of contact. Recipient is not usually converted to F+ since the F factor is nicked in the middle Crossing over can occur btw homologous regions. Conjugation
F factor excises out of a chromosome in a Hfr cell F′ plasmid now contains F factor and some genes from chromosome Enters F- bacteria Produces merozygotes – partially diploid F' Bacteria
Uptake of DNA and incorporation into chromosome or plasmid -Naturally occurring – dead bacteria -Artificially introduced Competent – cells able to take up DNA Transformation
bacteria that have incorporated foreign DNA Transformants
Many strains are avirulent Small and rapid reproduction Easy to culture Genome is single chromosome - haploid Wild-type are prototrophic E. Coli has model organism
DNA or RNA (single or double stranded) as genetic material Can not reproduce on their own Viral genetics
viral particles that infect bacteria Bacteriophages
Virulent phages Viral DNA is injected into host cell where it replicated, transcribed, and translated into more phages Host cell bursts open to release viral particles Cannot undergo binary fission Bacteriophage – lytic cycle
Temperate phages Phage DNA is incorporated into host genome – prophage Passed onto all progeny cells Can be transcribed and translated Can exit from host genome to enter lytic cycle Bacteriophages – lysogenic cycle
Any gene is transferred Generalized Transduction
Bacterial DNA is degraded Some may enter viral protein coat instead of viral genetic material Transducing phages Can become incorporated into new host’s genome Transduction- Lytic cycle
Few genes are transferred/genes near certain sites of chromosome Specialized Transduction
prophage enters at specific sites of host’s genome When prophage excises, it may do so imperfectly and bring some hot DNA with it Then introduced to new host Transduction- Lysogenic cycle
Single strand directly codes for viral proteins Positive strand RNA viruses
Must make complementary RNA strand, which then codes for proteins Negative strand RNA viruses
Incorporate into host genome Must make DNA from RNA Reverse transcriptase Makes cDNA from DNA or RNA template Enters host genome as a provirus Can be transcribed and translated Some retroviruses contain oncogenes Cause tumors Retroviruses
Three common genes gag -Proteins that make up viral protein coat pol -Reverse transcriptase -Integrase – allows for insertion into host genome env -Glycoproteins on viral surface
Centromere is centrally located; arms equal length Metacentric
Centromere is off center Submetacentric
Centromere is close to one end p arm has satellites (knobs on stalks) Acrocentric
Centromere is at one end Not present in humans Telocentric
Complete set of chromosomes arranged in homologous pairs Karyotype
Giemsa stain; most common Stains A-T rich regions G banding
Stains centromeric heterochromatin and portions of chromosomes with large sections of heterochromatin C banding
Stains G-C rich regions Gives opposite banding pattern of G banding R banding
UV light is used Same pattern as G banding Q banding
Types of chromosome mutations Chromosomal rearrangement, Aneuploidy, Polyploidy
Structure is altered Chromosomal rearrangement
Abnormal number of chromosomes Missing one or more/having one or more extra Aneuploidy
1 or more additional sets of chromosomes Polyploidy
Chromosome rearrangements (4 types) Duplications, Deletions, Inversions, Translocations
Section of chromosome is doubled Duplications
repeated segment is right after the original Tandem
repeated segment is located elsewhere on chromosome, or on a different chromosome Displaced
Sequence is inverted from the original sequence Reverse
During paring of homologous chromosomes, duplicated region loops out Offspring receive two copies of involved genes from parent with duplication, and a third copy of the other parent Duplications (Heterozygotes)
loss of a portion of chromosome Large deletions can be seen cytogenetically; microdeletions by FISH If the deleted region includes the centromere, entire chromosome will be lost Usually lethal in homozygous form Deletions
Normal chromosome must loop out during pairing Partial monosomy for all involved genes Deletions (Heterozygous)
Affects gene dosage Deletions - heterozygotes
Expression of mutant/recessive phenotype due to loss of normal/dominant copy Pseudodominance
Both copies of the gene are needed to manufacture adequate amount of gene product (One gene doesn’t produce enough for a normal phenotype) Haploinsufficiency
Two breaks in chromosome, then flipped and reinserted Inversions
Both breaks occur in one arm Paracentric inversion
Breaks on both arms; centromere is involved Can change morphology by altering centromere position Pericentric inversion
Disruption of a gene – no functional product Position effect (Change in gene position can affect gene expression) Inversions Effects
Chromosomes have to loop when pairing Inversion loops
If crossing over occurs within loop: Creates a dicentric chromosome and an acentric chromosome -Acentric is lost -Dicentric forms a dicentric bridge, and breaks -Nonviable recombinant gametes Paracentric inversion loops
Crossing over within loop creates recombinant chromosomes with duplications and deletions (nonviable) Pericentric inversion loops
Rearranges genetic material to another part of the same chromosome; or nonhomologous chromosome Translocations
Segment moves from one chromosome to another Nonreciprocal Translocations
Exchange between two chromosomes Reciprocal Translocations
Loss of gene function – break Position effect Creation of a fusion/abnormal protein Translocations Effects
Between two acrocentric chromosomes (13, 14, 15, 21, 22) 2 q arms are joined at a common centromere (Forms a metacentric chromosome if two chromosomes are same size) Small fragment is usually lost (acentric) Robertsonian translocation
Named after the chromosome that is the origin of the centromere Translocated chromosome
Have one normal copy of a chromosome, and one translocated one -During meiosis, all 4 chromosomes will associate -Can segregate 1 of 3 ways Translocated chromosome (Heterozygotes)
Both normals go to one pole; both translocated go to the other (balanced) Translocation segregation (Alternate)
Each pole gets one normal, and the opposite translocated Partial monosomies/partial trisomie (unbalanced) Translocation segregation (Adjacent 1)
Each pole gets both the normal and translocated of the same chromosome (Inviable; rare) Translocation segregation (Adjacent 2)
-Under certain conditions/culturing techniques, chromosomes develop breaks/restrictions at particular locations -Now routinely tested for by FISH analysis Fragile sites
Abnormal number of chromosomes Caused by: -Loss of chromosome during cell division; random error or loss of centromere; nondisjunction -Robertsonian translocation Aneuploidy
-Nullisomy 2n – 2 – missing both members of a homologous pair -Monosomy 2n – 1 – missing one chromosome -Trisomy 2n + 1 – one extra chromosome -Tetrasomy – 2n + 2 – two extra chromosomes of the same type/homologous Types of Aneuploidy
-Often lethal if constitutional Can see elaborate abnormalities in tumor cells -X inactivation in mammals takes care of extra Xs, so not as severe Aneuploidy
-Primary 3 free copies of #21 -Familial Extra copy due to translocation Down Syndrome (Aneuploidy)
Both chromosomes of a homologous pair from the same parent Probably originated from a trisomy (1 chromosome is lost early in development) Recessive diseases (One carrier parent and one normal parent can have an affected child) Uniparental Disomy
Nondisjunction in later development can cause “patchiness” – normal cells and abnormal cells Approximately 50% of Turner syndrome can be mosaics 45, XO/46, XX Mosaicism
Extra sets of chromosomes -Triploid – 3n; tetraploid – 4n Common in plants – more tolerant of extra sets of chromosomes Polyploidy
Extra set is from same species (attacking self) -Error in cell division Extra chromosome caused pairing problems; especially with odd numbers -3n usually sterile; produce small seeds Autoploidy
Hybridization between two species AABBCC x GGHHII F1 generation ABCGHI – not homologous -Gametes are inviable, but may be able to reproduce asexually Nondisjunction error can lead 2x, which could then reproduce sexually Allopolyploidy
DNA made up of 4 different nucleotides in equal amounts. DNA doesn’t have the variety needed for genetic material Tetranucleotide theory
Consisted of DNA and protein Nucleic acid
Protein is composed of __ different amino acids 20
A=T and G=C Chargaff's rule
What is the chemical nature of the transforming substance? DNA because only DNase destroyed transforming substance
Which part of the phage-its DNA or its protein-serves as the genetic material and is transmitted to phage progeny? DNA, not protein, is the genetic material in bacteriophages
Diffraction pattern Gives information on molecular structure
WHat substance-RNA or protein- carries the genetic material in viruses? RNA
Carbon in sugar can be referred to as # prime
Ribose RNA -OH at 2'carbon (less stable)
Deoxyribose DNA (removing an oxygen) -H at 2' carbon
Phosphorous and 4 oxygen Negatively charged Attached to 5′ carbon Phosphate group
Nitrogenous base Covalently bonded to 1′ carbon
two main types of Nitrogenous base Purine and Pyridine
Purine Double-ringed; six- and five-sided rings
Two types of Purine Adenine Guanine
Two types of Pyridine Cytosine Thymine (DNA only) Uracil (RNA only)
Single-ringed; six-sided ring Pyridine
RNA only Uracil and ribose
DNA only thymine and deoxyribose
Nucleoside base and sugar
Nucleotide Nucleoside + phosphate
DNTP Deoxy-nucleoside-tripphosphate
Nucleotides covalently bonded? phosphodiester bonds
Phosphate group of one nucleotide bound to ….. 3'C of previous sugar
Backbone consists of….. alternating phosphates and sugars
DNA double helix (antiparallel) 2 antiparallel strands with bases in interior Bases held together by hydrogen bonds
Backbone? Always has one 5′ end (phosphate) and one 3′ end (sugar –OH)
complementary strands Complementary base pairing??
Base pairing 2 between A and T (easy to pair); 3 between G and C
B-DNA (most common) Shape when plenty of water is present Right hand/clockwise turn; approx 10 bases per turn
A-DNA Form when less water is present; no proof of existence under physiological conditions Shorter and wider than B form Right hand/clockwise turn; approx 11 bases per turn
Z-DNA Left hand/counterclockwise turn Approx 12 bases per turn (narrower) Found in portions with specific base pair sequences (alternating G and C
Central dogma Replication, Transcription and translation
Created by: nenatweet24
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