Meiosis and Mendelian Genetics

Flashcards covering key concepts from the lecture on meiosis and Mendelian genetics.

Meiosis

A special type of cell division that cuts the genetic information of cells in half to produce gametes.

Gametes

Reproductive cells (sperm and eggs) that have half the genetic material of somatic cells.

Haploid Number (N)

One complete set of chromosomes, found in gametes.

Diploid Number (2N)

Two complete sets of chromosomes, typically found in somatic cells.

Homologous Chromosomes

Matching pairs of chromosomes, one from each parent, containing the same types of genes.

Zygote

The first cell formed when sperm and egg combine, containing a diploid set of chromosomes.

Crossing Over

The exchange of DNA between homologous chromosomes during prophase I of meiosis, increasing genetic variation.

Nondisjunction

The failure of homologous chromosomes to separate properly during meiosis, leading to gametes with abnormal chromosome numbers.

Trisomy 21

Also known as Down Syndrome; a chromosomal condition resulting from an extra copy of chromosome 21.

Mendel's Law of Segregation

During gamete formation, the two alleles for each trait segregate from each other so that each gamete carries only one allele for each trait.

Mendel's Law of Independent Assortment

The alleles for different traits are passed independently of one another during gamete formation.

Punnett Square

A diagram used to predict the outcome of a genetic cross by showing the possible combinations of alleles.

Allele

Different forms of a gene that can exist at a specific locus on a chromosome.

Homozygous

Having two identical alleles for a particular gene.

Heterozygous

Having two different alleles for a particular gene.

Phenotype

The observable physical or biochemical characteristics of an organism as determined by genetic makeup.

Genotype

The genetic constitution of an organism, representing the specific alleles inherited from parents.

Variable Expressivity

The degree to which a genotype is expressed in an organism.

Epigenetics

The study of how environmental factors can alter gene expression without changing the DNA sequence.

Rosalind Franklin's X-ray Diffraction

Rosalind Franklin's work provided critical X-ray crystallography images (Photo 51) that revealed major structural features of DNA, including its helical shape and dimensions, which were crucial for the discovery of the double helix structure.

Chargaff's Rules (1950)

Discovered by Erwin Chargaff, these rules state that in DNA, the amount of adenine (A) always equals the amount of thymine (T), and the amount of guanine (G) always equals the amount of cytosine (C).This crucial finding laid the foundation for understanding base pairing in the DNA structure.

Hershey-Chase Experiment (1952)