meiosis and karyotypes. somatic cells v. gametes 0 somatic – body cells 0 ex. skin, liver,...

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Meiosis and Karyotypes

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Page 1: Meiosis and Karyotypes. Somatic Cells v. Gametes 0 Somatic – body cells 0 Ex. Skin, liver, eyeballs 0 Gametes – sex cells 0 Ex. Egg or sperm (DNA here

Meiosis and Karyotypes

Page 2: Meiosis and Karyotypes. Somatic Cells v. Gametes 0 Somatic – body cells 0 Ex. Skin, liver, eyeballs 0 Gametes – sex cells 0 Ex. Egg or sperm (DNA here

Somatic Cells v. Gametes

0Somatic – body cells0 Ex. Skin, liver, eyeballs

0Gametes – sex cells0 Ex. Egg or sperm (DNA

here gets passed on to your kids!)

Page 3: Meiosis and Karyotypes. Somatic Cells v. Gametes 0 Somatic – body cells 0 Ex. Skin, liver, eyeballs 0 Gametes – sex cells 0 Ex. Egg or sperm (DNA here

0 We have 46 total. 0 We get 23 from mom, 23 from dad – so we have two pairs of

23. Get it?0 Each pair in the set is genetically identical, unless a

mutation occurs.0 Homologous chromosomes – two chromosomes (one

from ma, one from pop) that look the same, are the same length and HAVE THE SAME GENES.

Page 4: Meiosis and Karyotypes. Somatic Cells v. Gametes 0 Somatic – body cells 0 Ex. Skin, liver, eyeballs 0 Gametes – sex cells 0 Ex. Egg or sperm (DNA here

Autosome v. Sex Chromosome

0Autosomes – Contain genes not directly related to your sex.

0Humans have 44 (Chromosome pairs 1-22)

0Sex chromosomes – directly control development of sexual characteristics

0Pair #230Humans have two

options: X, Y0 XX = female0 XY = male

Page 5: Meiosis and Karyotypes. Somatic Cells v. Gametes 0 Somatic – body cells 0 Ex. Skin, liver, eyeballs 0 Gametes – sex cells 0 Ex. Egg or sperm (DNA here

Sexual Reproduction v. Asexual Reproduction

0 Remember we called mitosis a form of asexual reproduction. The cells are identical. We use it for growth and repair all the time!!

0 Sexual reproduction involves fusing two gametes to make a genetic MIXTURE of both parents.0 When human gametes fuse we call it fertilization.0 The nucleus of the egg (23 chromosomes) fuses with the

nucleus of the sperm (23 chromosomes) to make a new nucleus for a new individual (23+23 = ??)

Page 6: Meiosis and Karyotypes. Somatic Cells v. Gametes 0 Somatic – body cells 0 Ex. Skin, liver, eyeballs 0 Gametes – sex cells 0 Ex. Egg or sperm (DNA here

Diploid v. Haploid

0Diploid – cell has two copies of the chromosomes

0Also known as 2N0 In humans, 2N or diploid

= 460Somatic cells are diploid0Mitosis

0Haploid – cell has ONE copy of the chromosome

0Also known as 1N0 In humans, 1N or

haploid = 230Gametes are haploid0Meiosis

Page 7: Meiosis and Karyotypes. Somatic Cells v. Gametes 0 Somatic – body cells 0 Ex. Skin, liver, eyeballs 0 Gametes – sex cells 0 Ex. Egg or sperm (DNA here

Meiosis!

0Two cell divisions0Dividing the nucleus to make four HAPLOID cells that

are all genetically different0 Involved in sexual reproduction0During Prophase 1 of meiosis crossing over (the

exchange of genetic material between homologous chromosomes) occurs.

0Crossing over helps ensure genetic diversity

Page 8: Meiosis and Karyotypes. Somatic Cells v. Gametes 0 Somatic – body cells 0 Ex. Skin, liver, eyeballs 0 Gametes – sex cells 0 Ex. Egg or sperm (DNA here

Homologous chromosomes v. sister chromatids

0Homologous chromosomes – get one from mom and one from dad

0Similar length, carry same genes

0NOT copies of each other

0Divided in Meiosis 1

0Sister chromatid – chromatids attached by a centromere

0Divided in Meiosis 2

Page 9: Meiosis and Karyotypes. Somatic Cells v. Gametes 0 Somatic – body cells 0 Ex. Skin, liver, eyeballs 0 Gametes – sex cells 0 Ex. Egg or sperm (DNA here

Karyotype

0Picture of all the chromosomes in a cell, used to study chromosomes, help determine where genes are on chromosomes

0Show changes in chromosomes – like too many or too few

0Sometimes chromosomes don’t separate properly, this is called nondisjunction0 Down Syndrome – extra copy of chromosome #210 Can have extra chromosomes on any pair, even sex

chromosomes