Lecture #1 - Genetics & Chromosomes

Genes

Sections of DNA(sequence of nucleotide bases) that code for a specific protein (sequence of amino acids) and are expresssed as our phenotypes.

Alleles

Different forms of a gene- aka- different coding for a gene. For example, there are different alleles for hair genes such as curly vs straight hair.

chromosomes

packed doubled-stranded DNA that is located in the nucleus.

Made up of a double-stranded DNA + histones.

histone purpose

helps close, compactify, and organize DNA

autosomes vs sex chromosomes

Autosomes = 22 pairs, 1 pair of sex chromosomes. Male = XY (determines sex of offspring). Female = XX

homologous chromosomes (homologs)

in a diploid organism, chromosomes that are similar in size, shape, and gene content

-they can carry same sequence of genes(same loci) BUT they may be differen allels

-23 chromosomes from each parent from homologous chromosomes

centromeres

divides chromosome/chromatid into arms

locus (loci - plural)

the physical location of a gene on a chromosome

Ploidy

number of sets of chromosomes in a cell

(how many of the same chromosomes are in the cell?)

Haploid

Only 1 of each chromosome in each cell

-joined sister chromatids = 1 chromosome

Diploid

containing two complete sets of chromosomes, one from each parent.

Polyploid

condition in which an organism has extra sets of chromosomes

-eg. down syndrome or different animals

haploid number

Number of unique chromosomes in a gamate (sex cell), represented by n

(ploidy #)n = total chromosomes

unreplicated vs. replicated chromosome

Unreplicated = single molecule of double-stranded DNA, aka chromatid

Replicated = 2 identical chromatids (sister chromatids) with identical DNA

homologous chromosomes vs. sister chromatids

Homologous = same length/size/centromere but DIFFERENT ALLELES

sister = same length/size/centrmere with EXACT SAME ALLELES (DNA)

number of DNA molecules vs chromosome number

1 chromosome = 2 DNA molecules

ploidy versus haploid number

Ploidy = How many replicates of unique chromosomes

Haploid = How many uniques chromosomes

Heterozygous vs. Homozygous

Heterozygous - Two different alleles (Aa)
Homozygous - Two same alleles (AA or aa)