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 form _______________. When the chromosome first become visible, each chromosome consists of two identical ____________ joined by a ______________. chromosomes chromatids centromere

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

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 __________ cells. Each somatic cell contains 46 chromosomes or two sets of ______. The 23 different chromosomes differ in size, shape and __________________. A complete set of chromosomes is essential to survival. somatic 23 Set of genes

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

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

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

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 are ______________. Autosomes are not directly involved in determining the ______ of an organism. autosomes sex 1 through 22 = autosomes

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

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

Determining Gender In humans, a male’s sex chromosomes are written as ______ and a female’s sex chromosomes are written as ______. The sex (gender) of a human child is determined by the _________ parent. 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. XY XX male