Untitled Flashcards Set

linked genes: Genes located on the same chromosome that tend to be inherited together because they do not assort independently.
crossing over: The process during prophase I of meiosis where non-sister chromatids of homologous chromosomes exchange genetic material.
double crossover: An event where two separate crossover events occur between the same pair of homologous chromosomes.
recombinants: Offspring with a combination of alleles different from either parent due to crossing over.
synapsis: The pairing of homologous chromosomes during prophase I of meiosis.
chiasma/chiasmata: X-shaped structures that form between homologous chromosomes during crossing over.
non-sister chromatids: Chromatids from homologous chromosomes that are not identical but participate in crossing over.
synaptonemal complex: A protein structure that forms between homologous chromosomes during synapsis and facilitates recombination.
homologous recombination: The exchange of genetic material between homologous chromosomes during meiosis.
crossover recombinants: Chromatids resulting from the resolution of Holliday junctions in a way that results in the exchange of DNA between homologous chromosomes.
double-strand break model: A mechanism of homologous recombination where a double-strand break is repaired through DNA synthesis and resolution of Holliday junctions.
tetrad: A group of four chromatids (two homologous chromosomes, each consisting of two sister chromatids) formed during meiosis.
Holliday junctions: A cross-shaped structure formed during homologous recombination when strands of DNA exchange between homologous chromosomes.
recombination frequency: The proportion of offspring that are recombinants, used to measure the genetic distance between genes.
non-crossover recombinants: Chromatids where genetic loci outside the region of recombination remain unchanged despite crossing over occurring.

genetic linkage: The tendency of alleles that are close together on a chromosome to be inherited together during meiosis.
linkage map: A diagram showing the relative positions of genes on a chromosome, based on recombination frequencies.
map unit (centimorgan, cM): A unit of measurement for the genetic distance between genes, equivalent to a 1% recombination frequency.
physical map: A map of the physical distances between genes or markers on a chromosome, often measured in base pairs.
parental types: Offspring whose genotype matches one of the parental genotypes due to no crossing over occurring.
coupling (cis configuration): When two dominant or two recessive alleles are on the same homologous chromosome.
repulsion (trans configuration): When a dominant and a recessive allele are located on the same homologous chromosome.
heteroduplex DNA: A double-stranded DNA molecule formed during recombination that contains one strand from each homologous chromosome.
gene conversion: A process by which one allele is changed to another due to mismatch repair during recombination.
interference: The phenomenon where a crossover in one region of a chromosome reduces the likelihood of another crossover nearby.
positive interference: A situation where fewer double crossovers are observed than expected.
negative interference: A situation where more double crossovers are observed than expected.
molecular markers: DNA sequences that serve as landmarks for gene mapping, including SNPs, RFLPs, and microsatellites.
SNP (single nucleotide polymorphism): A variation in a single nucleotide that occurs at a specific position in the genome, often used in genetic mapping.
RFLP (restriction fragment length polymorphism): Variations in the length of DNA fragments produced by restriction enzymes, used as genetic markers.
microsatellites: Short, repetitive sequences of DNA that vary in length and are used as markers in genetic studies.
meiosis: A type of cell division that reduces the chromosome number by half, leading to the production of haploid gametes.
chromatid interference: The phenomenon affecting how chromatids participate in crossing over, though generally assumed not to occur in most species.
hotspot (of recombination): A region of the genome where the frequency of recombination is significantly higher than average.
coldspot (of recombination): A region of the genome with a lower-than-average frequency of recombination.
non-disjunction: The failure of chromosomes to separate properly during meiosis, resulting in aneuploidy.

Mendel's Law of Independent Assortment

when two or more characteristics are inherited, individual hereditary factors assort independently during gamete production, giving different traits an equal opportunity of occurring together.

Dihybrid Test Cross

Crossing an unknown genotype dominant individual with a known recessive to find out its genotypic makeup. Also proves independent assortment. 1:1:1:1

Bateson and Punnett

worked with peas, observed that some traits do not assort independently but they offered no explanation

Morgan (Linkage)

while working on Drosophila he observed non-independent assortment of two autosomal genes, purple and vestigial

Morgan's Discovery of Linkage

When crossing a heterozygous fly with a homozygous recessive fly (test cross); they expected a 1:1:1:1 ratio but did not get that. Instead they got most with the parents phenotype and some without the parents phenotype

linked genes

Genes located on the same chromosome that tend to be inherited together in genetic crosses.

DNA Recombination

rearrangement of DNA sequences by exchanging segments from different molecules

Chiasmata

The X-shaped, microscopically visible region representing homologous chromatids that have exchanged genetic material through crossing over during meiosis.

Homologus

_____ Chromosomes exchange genetic Material via Crossing over

Crossing Over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

Parental vs. Recombinant

Parental - same Phenotype as one of parents

Recombinant - different phenotype from either parent

Homologous Recombination

process that results in genetic exchange between homologous DNA from two different sources

Heteroduplex DNA

double-stranded DNA in which the 2 strands of the helix are derived from non-sister chromatids of homologous chromosomes

Double Stranded Break Model

- DNA synthesis

- 2nd end capture

- 2 Holliday junctions

- Holliday junction resolution

- Patch recombinant

- Splice recombinant

recombination between homologous chromosomes

generates new allele combinations

Genetic (Linkage) Mapping

process for creating maps of genes based on their linkage relationships to other genes

Recombination Frequency

RF = (# of recombinants)/(total # of progeny)

When Recombinants are under 50%

The genes are linked

When Recombinants are about 50%

We can not determine if the genes are linked or not

Proportional

Recombinant Frequency is _____________ to the distance between genes

More likely

The further apart 2 genes are, the ___________ it is that a crossover will occur between them to form recombinant chromosomes.

1% RF

1 map unit (m.u.) = 1 centiMorgan (cM)