3.3 + 10.3 meiosis

Question 1

mitosis produced _____ (type) cells while meiosis produces _____ cells

Answer 1

somatic, sex

Question 2

daughter cells produced from mitosis are genetically _________ to parent cell but that from meiosis are genetically ________

Answer 2

identical, dissimilar

Question 3

how many cell divisions are involved in meiosis?

Answer 3

2

Question 4

crossing over occurs during…

Answer 4

prophase I

Question 5

crossing over occurs between…

Answer 5

non-sister chromatids of a pair of homologous chromosomes

Question 6

homologous chromosomes pair up to form _______

Answer 6

bivalents

Question 7

bivalents are formed by _________ chromosomes

Answer 7

homologous

Question 8

a c______ is formed during crossing over

Answer 8

chiasma

Question 9

the site of attachment of homologous chromosomes during crossing over is called a _______

Answer 9

chiasma

Question 10

how does crossing over lead to genetic variation?

Answer 10

• during crossing over,
• genetic material is exchanged between non-sister chromatids
• new combinations of alleles are generated

Question 11

what occurs in prophase I of meiosis? (5)

Answer 11

• DNA supercoils → condensation of DNA
• nuclear envelope disintegrates
• centrioles migrate to the poles of the cells
• homologous chromosomes pair up
• crossing over between non-sister chromatids of homologous chromosomes

Question 12

when does independent assortment occur?

Answer 12

metaphase I

Question 13

how are paired homologous chromosomes oriented at the equator?

Answer 13

they are randomly oriented

Question 14

how is genetic variation generated? (3)

Answer 14

1. crossing over of non-sister chromatids during prophase I of meiosis
2. independent assortment of homologous chromosomes during metaphase I of meiosis
3. random fusion of gametes

Question 15

what is down syndrome caused by?

Answer 15

an extra copy of chromosomes 21

Question 16

how does down syndrome arise?

Answer 16

from non disjunction

Question 17

what phase of meiosis does non-disjunction occur at?

Answer 17

anaphase

Question 18

does non disjunction occur in meiosis I, II or both?

Answer 18

both

Question 19

how can genetic diseases be checked?

Answer 19

karyotype analysis

Question 20

what are two ways to extract fetal cells for karyotype analysis?

Answer 20

1. chorionic villus sampling (CVS)
2. amniocentesis

Question 21

where are the fetal cells from CVS from?

Answer 21

from the chorionic villi

Question 22

where are the fetal cells from amniocentesis from?

Answer 22

from the amniotic sac

Question 23

how is chorionic villus sampling carried out?

Answer 23

• a syringe with a long needle is inserted into mother’s abdomen to reach the placenta
• fetal cells are removed from the thechorionic villi** of the placenta
• guided by ultrasound

Question 24

how is amniocentesis carried out?

Answer 24

• a syringe with a long needle is inserted into mother’s abdomen and uterus wall
• sample of amniotic fluid containing fetal cells is removed from the amniotic sac
• guided by ultrasound