BIOL 121 Genetics

Alleles

Slightly different versions of the same gene

Chromatin

Complex of DNA + histone proteins that make up a chromosome

Epigenetic

How gene expression is altered by changing genome structure

Methylation

Genome tagging with CH3 (methyl) group that cause tight packing of the genome

Homologous chromosomes

Chromosomes that contain the same set of genes ± different alleles

Dominant allele

Allele with phenotype that appears in heterozygote

Recessive allele

Allele with phenotype that does not appear in heterozygote

Independent assortment

The observation that maternal and paternal homologs line up at random before separating at the end of Meiosis 1, producing a wide array of possible combinations in daughter cells

Gene

A segment of DNA that contains the information require to produce a product that functions in the organism

Transcription

The process that creates an RNA molecule from information stored in a gene

Translation

The process that uses the information in messenger RNA (mRNA) to synthesize a protein

Gene expression

The entire set of processes that results in using the information stored in a gene

Nucleosome

A group of eight histone proteins that has DNA wrapped around it

Histone proteins

Proteins that have an abundance of positively charged lysines and arginines in their primary structure, which interact with negative charges on the sugar-phosphate backbone of DNA to form nucleosomes

Homozygous

Having two copies of the same allele for a gene

Heterozygous

Having two different alleles for a gene

Ploidy

The number of copies of each type of chromosome present

Haploid number

The number of different types of chromosomes found in each cell of an organism, and is symbolized with an n. (eg, n=23)

Central Dogma

Gene → mRNA → Protein

Mitosis

A process in eukaryotes where chromosomes are copied in a parent (progenitor) cell which divides into two daughter (progeny) cells

M phase

The portion of the cell cycle when mitosis and cell division occur

Interphase

The portion of the cell cycle when growth and DNA replication occur

Prophase

The initial phase of mitosis, when replicated chromosomes condense and the nuclear envelope breaks down

Metaphase

The middle phase of mitosis, when replicated chromosomes move to the middle of the cell

Anaphase

The first late phase of mitosis, when sister chromatids separate and one of each type of chromosome ends up at either end of the parent cell

Telophase

The second late phase of mitosis, where the nuclear envelopes re-form around each set of chromosomes

Germ cells

Cells that directly give rise to sperm or eggs, or are sperm or eggs themselves. They undergo meiosis to produce haploid daughter cells

Somatic cells

Cells that form the body, and that only undergo mitosis

Meiosis

A process in eukaryotes that distributes one of each homologous chromosome pair to daughter cells, resulting in a halving of chromosome number

Gamete

Cells that fuse to form a zygote. In many species, these are sperm and egg

Zygote

A fertilized egg

Maternal chromosome

Any chromosome inherited from the mother

Paternal chromosome

Any chromosome inherited from the father

Crossing over and recombination

Physical exchange of DNA strands between non-sister chromatids during Meiosis 1. Leads to recombinant chromosomes containing alleles from both maternal and paternal chormosomes

Sexual reproduction

Production of offspring that is based on meiosis and fusion of gametes

Asexual reproduction

Production of offspring that is based on mitosis

Prophase 1

Homologs come together, and DNA will swap which produces a new combination of alleles not found in parents

Metaphase 1

Paired homologs line up at metaphase plate

Telophase 1

Homologs have separated, and each cell is now haploid with one homolog each

Anaphase 2

Sister chromatids separate but have half the chromatids