Week 05: Linkage, Maps, and Inheritance Patterns

linkage in genetics

refers to the tendency of genes that are located close to each other on a chromosome to be inherited together during meiosis.

Chi-Square Analysis

statistical method used to determine if there is a significant difference between the expected and observed frequencies in categorical data.

genetic map

representation of the arrangement of genes on a chromosome, indicating the relative distances between them based on recombination frequencies.

recombination frequency

the proportion of offspring that exhibit a combination of traits different from either parent, used to estimate the distance between genes on a chromosome.

What does a Chi-Square test measure

measures how expectations compare to actual observed data, helping to determine if any deviations are due to chance.

purpose of a genetic linkage map

to identify the location of genes on a chromosome and to understand the genetic basis of traits.

linkage disequilibrium

non-random association of alleles at different loci in a given population.

significance of a p-value in Chi-Square tests

indicates the probability of observing the data assuming that the null hypothesis is true; a low p-value suggests that the null hypothesis can be rejected.

null hypothesis in Chi-Square tests

states that there is no significant difference between the expected and observed frequencies.

phenotype

observable physical or biochemical characteristics of an organism, determined by both genetic makeup and environmental influences.

genotype

genetic constitution of an individual, representing the alleles inherited from both parents.

test cross

breeding experiment used to determine the genotype of an individual with a dominant phenotype by crossing it with a homozygous recessive individual.

genes are said to be 'linked'

genes are located close to each other on the same chromosome and tend to be inherited together.

difference between autosomal and sex-linked traits

Autosomal traits are controlled by genes located on non-sex chromosomes, while sex-linked traits are controlled by genes located on sex chromosomes.

Mendelian inheritance

refers to the patterns of inheritance first described by Gregor Mendel, based on the segregation and independent assortment of alleles.

monohybrid cross

genetic cross between parents that differ in only one trait, allowing the study of inheritance patterns for that trait.

dihybrid cross

genetic cross between parents that differ in two traits, allowing the study of the inheritance of both traits simultaneously.

significance of the Law of Segregation

states that during the formation of gametes, the two alleles for a trait segregate from each other, ensuring that offspring receive one allele from each parent.

significance of the Law of Independent Assortment

states that alleles for different traits are distributed to gametes independently of one another, leading to genetic variation.

pedigree chart

diagram that depicts the biological relationships between individuals in a family, used to analyze inheritance patterns of traits.

locus

specific physical location of a gene or genetic marker on a chromosome.

dominant allele

allele that expresses its phenotype even when heterozygous with a recessive allele.

recessive allele

allele that only expresses its phenotype when homozygous, meaning two copies are present.

purpose of using a Chi-Square test in genetics

to evaluate whether the observed frequencies of genotypes or phenotypes fit the expected ratios based on Mendelian inheritance.

significance of the 1:2:1 ratio in genetics

represents the expected genotypic ratio from a monohybrid cross between two heterozygous individuals.