Chromosomes PowerPoint

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Chromosomes

Chromosome Structure: 

Chromosome Structure When a cell is not dividing the DNA is loose, long, and skinny and is called chromatin . During cell division the DNA in a cell’s nucleus is coiled around proteins to form structures called chromosomes .

Chromosome Structure: 

Chromosome Structure histones

Chromosome Structure in Prokaryotes: 

Chromosome Structure in Prokaryotes Prokaryotic organisms like bacteria contain only one chromosome. This chromosome is always circular .

Chromosome Numbers: 

Chromosome Numbers Each species has a characteristic number of chromosomes. Humans for example have 46 chromosomes ( 23 pairs ).

Sex Chromosomes vs. Autosomes: 

Sex Chromosomes vs. Autosomes There are 2 kinds of chromosomes: Sex chromosomes Sex chromosomes - the chromosomes that determine the sex of the organism. In humans, the sex chromosomes are the X and Y chromosomes . Humans only have 2 sex chromosomes ( 1 pair ) out of the 46 total chromosomes (23 pairs) we have. Females = XX Males = XY Autosomes Autosomes - All other chromosomes that are not sex chromosomes. Humans usually have 44 autosomes ( 22 pairs ).

Homologous Chromosomes : 

Homologous Chromosomes Every cell has 2 copies of each autosome . One copy comes from each parent. These pairs are referred to as homologous chromosomes or homologues . (homologue means “same size”)

Karyotypes: 

Karyotypes A karyotype is a picture of the chromosomes in a cell. You can see that in this karyotype there are 22 pairs of autosomes and 1 pair of sex chromosomes. Homologous Pairs Boy or Girl??? Boy

Boy or Girl?: 

9 Boy or Girl? Y - Chromosome X - Chromosome The Y Chromosome Decides

Most Cells are Diploid: 

Most Cells are Diploid In humans, all cells except sex cells are called diploid because there are two copies of each chromosome. The abbreviation for diploid is 2n (= 2 sets of chromosomes in homologous pairs)

Haploid Cells : 

Sex cells - sperm and egg cells All sex cells are called haploid because they have 1 copy of each chromosome; Chromosomes are not in homologous pairs . The abbreviation for haploid is 1n (= 1 set of chromosomes not in homologous pairs) Haploid Cells

Fertilization Results In A Diploid Zygote: 

In humans, all sex cells are haploid cells. When sperm ( 1n ) and egg ( 1n ) combine, they create a fertilized egg called a zygote which is a diploid (2n) cell (and will eventually grow into a baby through cell division!) Fertilization Results In A Diploid Zygote

Fertilization Results In A Diploid Zygote: 

Egg 1n Haploid nucleus Fertilization Results In A Diploid Zygote Sperm 1n Haploid nucleus

Fertilization Results In A Diploid Zygote: 

Sperm 1n Fertilization Results In A Diploid Zygote Egg 1n Haploid nucleus Haploid nucleus

Fertilization Results In A Diploid Zygote: 

Sperm 1n Fertilization Results In A Diploid Zygote Egg 1n Haploid nucleus Haploid nucleus

Fertilization Results In A Diploid Zygote: 

Sperm 1n Fertilization Results In A Diploid Zygote Egg 1n Haploid nucleus Haploid nucleus

Zygote: 

Zygote Zygote 2n 2n