Lecture 6

Question 1

cytogenetics

Answer 1

they study of chromosomes with relation to cell behaviour

Question 2

Chromatin

Answer 2

uncondensed DNA

dna and proteins (histones)

Question 3

Euchromatin

Answer 3

active
loosely arranged

Question 4

Heterochromatin

Answer 4

inactive
densely arranged

Question 5

before cell division

Answer 5

chromosomes replicate, 2 identical copies that remain attached at the centromere

Question 6

Mitosis purpose

Answer 6

growth and repair

Question 7

Meiosis purpose

Answer 7

gamete formation

Question 8

interphase

Answer 8

chromosomes duplicate
centrosomes with centriole pairs

Question 9

prophase I

Answer 9

homologous chromosomes pair and exchange segments

spindle fibres start to form

Question 10

metaphase 1

Answer 10

tetrads line up

microtubules connect to chromosomes

Question 11

anaphase 1

Answer 11

pairs of homologous chromosomes split up

sister chromatids remain attached

homologous chromosomes separate

Question 12

Telophase 1 and cytokinesis

Answer 12

two haploid cells form: chromosomes are still double

cleavage furrow forms (dip between two joined cells)

Question 13

Meiosis 2

Answer 13

during another round of cell division the sister chromatids finally separate and four haploid daughter cells and formed

Question 14

2 mechanisms of producing new combinations of gametes

Answer 14

independent assortment

crossing over

Question 15

indepedant assortment

Answer 15

there are two equally probrable but different arrangements of chromomses at metaphase 1 so after meiosis 11 four gene combinations are created

Question 16

crossing over

Answer 16

exchange of maternal and paternal DNA during prophase 1

Question 17

Tetrad

Answer 17

group of four chromosomes

Question 18

Aneuploidy

Answer 18

loss or gain of a chromosome

usually not survivable

gain of chromosome 21 is survivable

Question 19

Nondisjunction

Answer 19

the failure of homologous chromosomes or sister chromatids to separate properly during cell division
- this leads to there being not enough or too many chromosomes in each gamete

Question 20

Karyotyping

Answer 20

the collection of chromosomes in a cell is the karyotype

arrange chromosomes by size, morphology and banding to make a karyogram

Question 21

Karyogram

Answer 21

a visualisation tool used to easily show the karyotype

Question 22

Down syndrome

Answer 22

Where someone has 3 copies of chromosome 21

this is the most common form on aneuploidy in live birth

physical growth delays, intellectual disabilities and poor immune function

Question 23

sex chromosome aneuploidies

Answer 23

better tolerated than autosomal aneuploidies

Question 24

XY karyotype aneuploidies

Answer 24

loss of Y (XO)- turners syndrome
Gain of Y XXY
loss of x YO- not survivable
Gain of X- XXY- kleinfelters syndrome

Question 25

Polyploidy

Answer 25

extra set of all chromosomes

very common in plants but rare in animals