Cell Reproduction Cell Reproduction Chromosomes 4 3 Each

Cell Reproduction

Cell Reproduction – Chromosomes 4. 3 • Each type of organism has a specific chromosome number. • Fly 8 Corn: 20 Dog: 78 Human: 46

Chromatin in Interphase • During interphase the chromosomes are not visible. • The DNA appears as a mass in the nucleus; the mass is called ______. chromatin

Chromosome in M-Phase • As the M phase begins the DNA coils up to chromosomes form ________. • When the chromosome first become visible, each chromosome consists of two chromatids identical ______ joined by a _______. centromere

chromatid • One half of a duplicated chromosome is a chromatid. • Sister chromatids are held together at the centromere. Sister chromatids centromere

Now go to your Biology handout pages 120 -124 to complete the next set of questions:

Body Cells • Every cell in the human body other than sperm and egg cells are called somatic _____ cells. • Each somatic cell contains 46 23 chromosomes or two sets of ______. • The 23 different chromosomes differ in Set of genes size, shape and _________. • A complete set of chromosomes is essential to survival.

Chromosomes • Each of the 23 pairs of chromosomes homologous consists of two _______ chromosomes (AKA homologues). • Each homologue in a pair comes from one parents of the two ______. Therefore, the 46 chromosomes in somatic cells are actually 2 sets of 23 chromosomes, one set from the ______ and one set mother father from the _______.

Chromosomes • When a cell contains two sets of diploid chromosomes it is said to be _____. 2 n • Diploidy is represented as _______. • In humans, the diploid number is _______. 46

Sex Cells gametes • The sex cells, also called ______, have only 1 set of chromosomes. • Gametes are ______. haploid n • Haploid is represented by ____. 23 • In humans, the haploid number is _____.

Sex Cells Why does it make sense that gametes have the haploid number of chromosomes? • sperm (23 chromosomes/1 set) + egg (23 chromosomes/1 set) = human zygote (46 total chromosomes) ***The human zygote is diploid

Chromosomes Of the 23 pairs of human chromosomes, 22 autosomes are _______. Autosomes are not directly involved in determining the sex of an organism. ______ 1 through 22 = autosomes

Determining Gender • There is 1 pair of chromosomes that will determine the sex of the sex organism called _____ chromosomes. • In humans and many other organisms, these two chromosomes are referred to as _____ and X _____ chromosomes. Y

Determining Gender • The genes that cause a fertilized egg to develop into a male are located on the Y _____ chromosome. • An organism with a _____ chromosome is Y Y male, and without a _____ chromosome the organism is ______. female

Determining Gender • In humans, a male’s sex chromosomes XY are written as ______ and a female’s sex chromosomes are written as ______. XX • The sex (gender) of a human child is determined by the _____ parent. male • Why? – Females have only XX to donate, but males may donate the X or Y; so males determine whether a male or female is produced.