heredity

lecture 13

What is heredity?

passing on of genes and genetic traits from parents to their offspring

What is genetics?

The study of how genetic traits are passed on from parents to offspring

What are genes?

Segments of DNA located on chromosomes that serve as heritable units and provide genetic instructions for human functions and traits, including physical features

How can mutations in genes affect offspring?

Mutations can be inherited, causing a predisposition to certain diseases

What is the genome?

All of an organism's genes and genetic material

How is the human genome packaged?

Into 23 pairs of chromosomes (n=46

Where are chromosomes inherited from?

Each chromosome is inherited from both fathers and mothers

What is the composition of human somatic cells in terms of chromosomes?

They contain 22 pairs of autosomes (which are homologous chromosomes) and 1 pair of sex chromosome

What are the sex chromosomes for females and males?

Homologous for females (XX) and non-homologous for males (XY)

What is a gene locus

The position or site of a gene on a chromosome

What is an allele?

A variant form of a gene at a chromosome locus

How do alleles typically occur?

pairs although multiple alleles may exist at a locus

What is genotype?

: A set of genes in DNA responsible for particular traits or characteristics

What is phenotype?

The physical observable properties arising from the genotype, such as physical appearance, morphology, development, and behaviour

What does each pair of alleles represent?

The genotype of a specific gene

How are genotypes described based on their alleles?

As HOMOZYGOUS (having 2 identical alleles for a given trait) or HETEROZYGOUS (having 2 different alleles for a given trait

How do alleles contribute to an organism's phenotype?

They can be either a DOMINANT allele (fully expressed in the phenotype) or a RECESSIVE allele (completely masked in the phenotype)

Using the example of eye colour (B=brown, b=blue), what are the genetic representations for homozygous dominant, homozygous recessive, and heterozygous genotypes?

◦Homozygous dominant: BB

◦Homozygous recessive: bb

◦Heterozygous: Bb

who is father of genetics

gregor mendel (pea plant)

What are monohybrids, dihybrids, and trihybrids?

Hybrids created by cross-pollination between parents differing in one, two, or three traits,

State Mendel's 1st Law of segregation.

The characteristics of an organism are controlled by alleles occurring in pairs. During meiosis these pairs of alleles segregate (separate) so that each gamete receives only one allele from each pair

What is a monohybrid cross?

A simple cross between two genotypes for a single trait

What are the key features of single-gene inheritance (Principal of segregation)?

1.Genes come in pairs; a cell/individual has two copies (alleles) of each gene.

2.Alleles for a pair of genes may be identical (homozygous) or different (heterozygous).

3.Each reproductive cell (gamete) contains only one allele of each gene

4.in gamete formation, any given gamete is equally likely to include either allele (e.g., from Ww, half gametes get W, half get w).

5.The union of male and female reproductive cells is a random process

What is a Back cross or Test cross designed to reveal?

The genotype of an organism that exhibits a phenotypically dominant trait

How is a Test cross performed?

Cross the unknown genotype with a homozygous recessive genotype