4.1-Cell Division & Genetic Material cont’d: Chromosomes and Karyotypes SBI3U

Asexual Reproduction Reproduction requires only one parent ▫ produces genetically identical offspring. Single-cell organisms can reproduce asexually through mitotic division (ie. Bacteria, protists, fungi)

Sexual Reproduction Two parents give rise to an offspring Offspring have a unique combination of genes from both parents Offspring is genetically distinct from siblings and parents

Sexual Reproduction Cont’d Requires fusion of male and female gametes GAMETE: male or female reproductive cell (i.e. egg or sperm) When the male and female gamete join (fertilization), a ZYGOTE is formed.

Chromosomes Human Somatic Cells ▫ 46 chromosomes (23 from each parent) Each chromosome is paired ▫ one chromosome from the father and one from the mother. maternalpaternal

Chromosomes Cont’d 1 of the 23 pairs of chromosomes are called sex chromosomes, the remaining pairs are called autosomes Sex chromosome: an X or Y chromosome that determines the genetic sex of an organism. Females: XX Males: XY

Chromosomes Cont’d sex chromosomes

Homologous Chromosomes Pairs of chromosomes that appear similar. Similarities: ▫ length ▫ centromere location ▫ banding patterns Each chromosome has genes (sections of DNA) ▫ Genes contain specific genetic information for traits

Similarities: 1)Length 2)Banding patterns (genes) 3)Centromere location

Homologous Chromosomes

Homologous Chromosomes Cont’d Homologous chromosomes have several characteristics in common. However, they are not identical They can carry different forms of the same gene, called alleles. The different alleles allow the variation in the population.

GENEALLELE Section of DNA that controls a specific trait. Ex. eye colour, blood type, skin colour Specific variation of a gene. Ex. blue eyes, green eyes, type A blood, black skin, white skin

Examining Chromosomes… Karyotype is a photograph used to examine pairs of homologous chromosomes in a cell Cell sample is collected and stopped during metaphase The sample is stained and viewed under a microscope

Karyotype Chromosomes are ordered from largest to smallest, and paired with other chromosomes that have the same banding pattern Autosomes are numbered from Sex chromosomes are identified as X or Y A B C DE FG

Why study karyotypes? Karyotypes help to determine chromosome abnormalities Can indicate genetic disorders such as Down syndrome or Turner syndrome..

Check your Understanding… Identify the abnormalities in the following karyotypes…

Homework Read pgs Complete pg. 168 Q# 1, 4, 5, 9, 14, 17 Karyotype Assignment