Seminar 15: Transmitting genetic information at a single gene locus

Question 1

Why is Meiosis I called the “reductional division?

Answer 1

It halves the number of chromosomes in the resulting cells compared to the parent cell (diploid 2n > haploid n)

Question 2

How does meiosis provide diff genetic combinations?

Answer 2

Due to crossing over, where homologous chromosomes exchange genetic material, leading to new combinations of alleles and increased genetic diversity.

Question 3

differentiate b/w Mitosis & Meiosis

Answer 3

Mitosis: somatic cells, separation of sister chromatids, 4 stages. PROD = 2 IDENTICAL DIPLOID daughter cells

Meiosis: Germ line cells, 4 stages split into 2 divisions, PROD = 2 NON-IDENTICAL HAPLOID daughter cells

Question 4

differentiate b/w Meiosis II & Meiosis II

Answer 4

1: reductional division. Reduced chromosome # (2n > n), resulting in 2 haploid daughter cells

2: equational division (sister chromatids separated), separates the duplicated genetic material w/in each chromosome, results in 4 haploid gametes

Question 5

How does the Law of segregation relate to the partitioning of chromosomes during meiosis?

Answer 5

• Law of segregation states that during the formation of gametes, the 2 alleles for a trait separate
• each gamete contains only one allele for each trait
• So segregation assures that each gamete receives only 1 allele of a gene
• causes genetic diversity in the offspring

Question 6

gametes contain only a ____ set of chromosomes

Answer 6

SINGLE

Question 7

2 haploid gametes fuse in fertilisation to form a ____

Answer 7

ZYGOTE

Question 8

the prod of meiosis are ______ _____ from 1 another & from the parent cell

Answer 8

GENETICALLY DIFFERENT

Question 9

3 main effects of meiosis

Answer 9

1. reduce # of chromosome # from diploid (2n) to haploid (n)
2. ensures that each of the haploid prod has a complete set of chromosomes
3. generates genetic diversity among the products

Question 10

meiosis consists of ___ nuclear divisions

Answer 10

2

Question 11

2 unique features of the 1st meiotic nuclear division

Answer 11

1. homologous chromosomes come together to PAIR along their LENGTHS
2. homologous chromosome pairs SEPARATE but the individual chromosomes (each w/ 2 sis chromatids) remain intact

Question 12

what precedes meiosis 1 (similar to mitosis)

Answer 12

Interphase w/ an S phase where each chromosome is replicated

Question 13

when do the 2 sister chromatids separate?

Answer 13

meiosis 2, anaphase 2

Question 14

prod of the 2 meiotic divisions:

Answer 14

4 haploid cells, not genetically identical

Question 15

what does a chiasma reflect?

Answer 15

exchange of genetic material b/w non-sister chromatids on homologous replicated chromosomes (crossing over)

Question 16

crossing over results in _____ ______

Answer 16

RECOMBINANT CHROMATIDS

Question 17

during meiosis, homologous chromosomes separate by ______ ______

Answer 17

INDEPENDENT ASSORTMENT

Question 18

what are the 2 reasons for genetic diversity among the products of meiosis?

Answer 18

• independent assortment
• crossing over

Question 19

____ ____ in meiosis 2 contributes further to genetic diversity of the meiotic products

Answer 19

CHANCE ASSORTMENT

Question 20

nondisjunction results in production of ____ ___

Answer 20

ANEUPLOID CELLS

Question 21

examples of nondisjunction

Answer 21

• failure of homologous chromosomes to remain attached in metaphase 1
• migration of homologous chromosomes to same pole in anaphase 1

Question 22

what is aneuploidy

Answer 22

condition where 1 or a few chromosomes are lacking or in excess

Question 23

desc translocation

Answer 23

process where a piece of chromosome may break away & become attached to another chromosome

Question 24

how does independent assortment increase genetic diversity

Answer 24

• homologous chromosomes are separated randomly
• each gamete receives a unique assortment of genetic material