• Defined: Tightly coiled DNA
• Forms during cell division– New chromosomes
created for new cells
• 2 Parts:
– 1) Chromatids: two identical parts of a chromosome
– 2) Centromere: Joins chromatids together
• Defined: Picture of an individuals chromosomes– Identify sex & chromosome
defects
• Size of final pair identifies sex– Same size: XX = female
– Different size: XY = male
• Normal human will have 46 chromosomes
• Diploid Cells = Cells with the full set of chromosomes– Paired chromosomes
• Half of our chromosomes come from each parent (23 from each parent)
• Somatic (non-sex) cells are diploid
• Created by mitosis• Ex: Skin, Muscle, Nerve,
Blood Cells
Humans have 46 total chromosomes. What is the human diploid chromosome number?
Remember…Diploid = total number of chromosomes
Answer = 46
Humans have 46 total chromosomes. What is the human somatic chromosome number?
Remember…Somatic cells are non-sex cells…
…Somatic cells are diploid…
…Diploid cells have the full set of chromosomes
Answer = 46
Humans have 46 total chromosomes. How many chromosomes are in brain cells?
Remember…Brain cells are non-sex cells…
…Somatic cells are non-sex cells…
…Somatic cells are diploid…
…Diploid cells have the full set of chromosomes
Answer = 46
• Haploid Cells = Cells with ½ the total number of chromosomes
• Gametes (sex cells) are the only haploid cells– Ex: Sperm, Egg, Pollen
• Chromosome number is reduced by meiosis
• How do humans get 46 chromosomes?
Haploid sperm cell (23) + Haploid egg cell (23) = Diploid zygote (46)
Humans have 46 total chromosomes. What is the human haploid chromosome number?
Remember…Haploid = half number of chromosomes
Answer = 23 chromosomes
Humans have 46 total chromosomes. What is the human gamete chromosome number?
Remember…Gamete cells are sex cells…
…Sex cells are haploid…
…Haploid cells have ½ the set of chromosomes
Answer = 23
Humans have 46 total chromosomes. How many chromosomes are in female egg cells?
Remember…Egg cells are sex cells…
…Sex cells are gametes…
…Gamete cells are haploid…
…Haploid cells have ½ the set of chromosomes
Answer = 23
Down Syndrome: What’s Wrong?
• Writing notation:– 1st: total
chromosome #– 2nd: Sex
chromosomes– 3rd: extra or
missing
• Down Syndrome: 47, XY, +21
Turner’s Syndrome: What’s Wrong?
• Write the notation for Turner’s Syndrome.
45, X, -23
or
45, XO, -23
Patau’s Syndrome: What’s Wrong?
• Write the notation for Patau’s Syndrome.
47, XY, +13
Klinefelter’s Syndrome: What’s Wrong?
• Write the notation for Klinefelter’s Syndrome.
47, XXY, +23
• What is the diploid chromosome number?
42
• What is the haploid chromosome number?
21
• How many chromosomes would be in somatic cells?
42
• How many chromosomes would be in brain cells?
42
• How many chromosomes would be in gamete cells?
21
• How many chromosomes would be in egg cells?
21
• How many chromosomes would be in muscle cells?
42
• How many chromosomes would be in sperm cells?
21
• Is this a male or female rat?
male
Quick Review• Chromsomes are tightly coiled
strands of DNA
• Diploid (somatic) cells contain the entire set of chromosomes
• Haploid (gametes) cells contain only ½ the total number of chromosomes
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