Genes Flashcards
Population genetics
Study of the gene pool of a population over time
Molecular genetics
Study of the molecular structure and function of genes
Cell cycle
Period between birth of a cell & its division into 2 daughter cells.
Prophase early
Mitotic spindles form from centrosomes
Chromosomes condense
Prophase later
Nuclear envelope breaks down
Chromosomes attach to mitotic spindle
Metaphase
Chromosomes line up at equator
Sisters chromatids attached to opposite poles of mitotic spindle
Anaphase
- Cohesion between sister chromatids lost
- Chromatids segregate to opposite poles, driven by shortening microtubules
Telophase
- Chromosomes decondense
- Nuclear envelope reforms
- Cytokinesis begins
Meiosis I
- Divides chromosome pair
- REductional division
- 2 haploid daughter cells
Meiosis II
- Divides sister chromatids
- Equational division
- 4 haploid gametes
Prophase I
- Chromosomes condense
- Synapsis of homologous chromosomes
- Crossing over occurs
Metaphase I
- Homologous chromosome pairs line up at equator
Anaphase I
- Homologous chromosomes separate to opposite poles
Telophase I
- Each pole has one original homologous chromosome
- Each chromosome still consists of two chromatids
- Cytokinesis completes meiosis I
At which stage of meiosis are homologous chromosomes separated?
Anaphase I
In humans, how many bivalents can be seen at prophase I of meiosis?
23
bivalents = haploid number
Mice have a diploid chromosome number of 40. How many chromatids are present at each cell at metaphase II of meiosis?
40 chromatids
Penetrance
Measure of the percentage of individuals with a given genotype who exhibit the expected phenotype
Why is the domantic white W allele epistatic to all other coat colour genes?
Dominant, LOF mutation in c-kit, is required for proliferation + migration of melanocytes
c-kit
Transmembrane growth factor receptor for tyrosine kinase protein
Expressivity
measure of the extent to which a given genotype is expressed at the phenotypic level
Transposable element
Piece of DNA which can move about the genome
Allelic variation
Alleles may vary in severity of phenotypes they cause, e.g. cystic fibrosis
How does the SRY gene confer maleness?
Transcription factor used to regulate gene expression necessary for testes formation.
Barr body
Inactivated condensed form of second X chromosome present in females.
True/False?
A linkage map is based on recombination frequencies
True
T/F?
Linked alleles stay together at meiosis
True
T/F?
Unlinked genes undergo independent assortment at meiosis
True
T/F?
Crossing over never occurs between linked genes
False
Endosymbiotic theory explains the presence of what structures in eukaryotic cells?
Mitochondria and chloroplasts
Most common type of DNA polymorphism in the human genome is
SNP’s
Types of aneuploidy
Nullisomy
Monosomy
Trisomy
Tetrasomy
Nullisomy
Loss of pair of homologous chromosomes (2n-2)
No viable birth in humans
Monosomy
Loss of single chromosome (2n-1)
Trisomy
One extra chromosome (2n+1)
Tetrasomy
An extra pair of chromosomes (2n+2)
How does anueploidy arise?
Non disjunction during meiosis
Down syndome
Trisomy 21 or
Robertsonian translocation
Genetic mosaicism
Patau syndrome
Trisomy 13
Edwards syndrome
Trisome 18
Robertsonian translocation
Can cause down syndrome
Translocation of chromosome 21 and 14
Disorders resulting from monosomy of sex chromosomes
Turner’s syndrome, XO (45, X)
Disorders resulting from trisomy of sex chromosomes
Klinefelter syndrome (47, XXY) Triplo-X (47, XXX) XXY syndrome (47, XXY)
Considering chromosome inactivation, why is phenotype still expressed in aneuploidy individuals?
Not all genes on inactive X are switched off, genes in PAR shared by X and Y arent inactivated causing greater expression.
Pseudoautosomal region
Small terminal region of homologous sequences on X and Y chromosomes which pair and recombine during meiosis.
High heritability means genetic determination.
True/False?
FALSE
e.g. height has increased over the population in the past 100 years, NS wont act that quickly, due to lifestyle changes
Differences between groups for traits with high heritability are the result of genetic differences.
True/False?
FALSE
e.g. difference in IQ found between African Americans and White Americans isn’t necessarily due to genetic differences
Kinetochore
mutiprotein complex that assembles at the centromere of a chromosome and is the site where microtubules attach
Karyotype
set of chromosomes in an individual
SRY gene
COnfers maleness in mammals
Non disjunction
Failure of chromosomes or sister chromatids to separate properly during meiosis
Synapsis
pairing of two homologous chromosomes
Variable expressivity
When individuals w/ the same genetic mutation show different levels of expression of the phenotype. Can be due to effects of modifier genes that differ between individuals, or due to environmental effects.
Endosymbiont theory
Hypothesis that mitochondria and chloroplasts originated as free-living prokaryotes that invaded a primitive eukaryotic cell
cambrian explosion
500 mil years ago
Fitness is
Measured by the number of surviving offspring produced by individuals of a specific genotype.
Average reproductive success of individuals with a specific genotype
position cloning
Molecular cloning of a gene on the basis of its position on the chromosome
recombinant type individual
Individual that has a non-parental combination of genetic markers as the result of crossing-over or independent assortme
Pleiotropic
Genes or mutations that affect multiple phenotypes
Epistasis
Interaction between two or more genes that control a single phenotype
Genomic imprinting
When either the maternal or paternal allele is not expressed in the offspring
Hemizygous
XY male who has one copy of a mutant allele on the X chromosome
SNP
difference in one base pair at a particular site in the genome
STR
site in the genome that consists of variable numbers of short repeated sequences
Modifier genes
Genes which influence the expression of another.
THink epistasis
