exam 1: chromosonen theory of inheritance

Question 1

what is the chromosome theory of inheritance?

Answer 1

Chrososomes carry genes=>chromosomes carry genetic information

-early evidence: chromosome movement during meiosis parallels
the behavior of Mendel’s “genetic particles”

Question 2

what kind of resides in the nucleus?

Answer 2

only equal contribution both sexes to make offspring in the nucleus

Question 3

what happens during meiosis and mitosis?

Answer 3

nuclear division
mitosis:
what happens to chromosomes?
replicated—>separated
how many chromosomes?
same #

meiosis:
what happens to chromosomes?
replicated–>separated–>separated
how many chromosomes? 1/2 of orginal #

n=# chromosomes in gamete (haploid)
2n=# chromosome in somatic cells of diploid organisms

Question 4

*what does a metacentric chromosome look like

Answer 4

has centromere near the center
=looks like an X

Question 5

*what does a acrocentric chromosome look like

Answer 5

has centromere close to the end
=looks like a Y

Question 6

What are centromeres and why are they important?

Answer 6

what: site for attachment of spindle fibers

why: keep sister chromatids tgt

Question 7

*sister chromatids

Answer 7

copies of exactly the same exact chromosome (from same parent)

Question 8

*homologous chromosomes

Answer 8

contain same set of genes but come from different parents (may have different alleles)

Question 9

*nonhomologous chromosomes

Answer 9

2 completel diff chromosomes carrying different genes

Question 10

what are karyotypes

Answer 10

-being used to study physical shape of chromosome
-arrange by size, shape, stained banding pattern, and placement of centromere

autosomes: matching pairs of non-sex determining chromsomes

sex chromosomes: non-matching (males), sex determining chromosomes

Question 11

how does sex determination supports chromosome theory of inheritance

Answer 11

-walter sutton
-lubber grasshopper
-only males developed from sperm with Y chromosomes
->if sex is determined by chromosomes, other traits are determined by chromosomes as well

Question 12

aneuploidy

Answer 12

abnormal # of chromosomes (1 or few)
-XXY (extra X)/ XO

Question 13

what cause anepoidy?

Answer 13

after recombination (crossing over) in meiosis I, they are supposed to split apart and switch part to give new unique genetic material

-howvever, NONdisjunction happens
->causing homologous chromosomes to fail to separate
=> 1 daughter cell ends up with extra chromosome and 1 ends up with no copies of that chromosome

Question 14

what can nondisjunction cause

Answer 14

can result in
1. Klinefelter’s
2.Turners
3. Down
-80% result due to nondisjunction by mother when making eggs
-risk in mother increases w age

Question 15

is segregation of homologous chromosomes random?

Answer 15

yes
-every homologue have an equal chance of going to either pole during anaphase

2^23 unique gametes can be made due to recombination which is why siblings dont look alike

Question 16

**Oogenesis

Answer 16

gametogenesis in females

cytokinesis asymmetric in meiosis I:
-1 daughter cell gets 95% od cytoplasm; the other daughter cell gets 5% (polar body)
why the asymmetric? put more surving material for a fetus to ensure the survival of the egg= ADVANTAGE (bc packing full of proteins)

-the oocyte undergo meiosis II but the sister chromatids gets arrested at metaphase II where they are physicallt connected
=>means meiosis II is NOT complete until fertilization
==>which means that chromosomes are stuck tgt for decades before they are fertilize,which mean the risk of nondisjunction is high as there is a high chance that they wont separate properly

Question 17

**Spermatogenesis

Answer 17

gametogenesis in males
1 prime sperms: 2^n germ cells —-mitosis—> 2^n (2 of them)-symmetric cytokinesis

2 prime sperms undergo symertric meisosi II to produce 4 haploid spematids
2^n—meisos—>1/2