numerical chromosomal abnormalities

Question 1

define mitosis

Answer 1

cell division where somatic cells are produced

Question 2

define meiosis

Answer 2

cells division where gametes are produced

Question 3

what are the 3 main stages of mitosis cell division

Answer 3

1. interphase = replication of chromosomes
2. mitosis = all body cells, two daughter cells made (46 chromosomes)
   PMAT

prophase = chromosomes condense and become visible. sister chromatids are pulled to opposite ends

metaphase = sister chromatids are lined up in pairs at the centre of the cell spindle

anaphase = sister chromatids pulled apart to opposite ends of the cell

telophase = nuclear membrane forms around each set of chromosomes. chromosomes uncoil and become less visible

3. cytokinesis = cytoplasm divides = 2 genetically identical daughter cells are formed

Question 4

explain meiosis

Answer 4

sperm fuses with egg = both sets of chromosomes combine to produce 46 chromosomes

meiosis 1 = reduction to 23 chromosomes - replication and recombination occurs

meiosis 2 = sister chromatids separated = 4 daughter cells, each with 23 chromosomes

gamete number of chromosomes is always haploid = 23

Question 5

explain segregation process

Answer 5

separation of chromatids/pairs of homologous chromosomes

both sister chromatids go to one pole = non disjunction

if this occurs in meiosis, gametes are chromosomaly unbalanced
resulting foetus has too many/few chromosomes

Question 6

describe ploity and anaploity

Answer 6

ploity = wrong number of whole sets of chromosomes

anaploity = single extra or missing chromosome e.g Turner’s

Question 7

describe karyotype, metacentric, submetacentric, Acrocentric

Answer 7

karyotype = humans have 23 pairs of chromosomes

metacentric = p and q arms even length

submetacentric = p arms shorter than q

Acrocentric = long q, small p

Question 8

define polypoid and aneuploid

Answer 8

polypoid = multiple numbers of haploid number

aneuploid = chromosome number which isn’t exact multiple of haploid number. occurs due to extra/missing chromosomes

Question 9

describe meiotic non disjunction

Answer 9

error in segregation of chromosomes

either in pairs of homologous chromosomes

Question 10

describe recombination

Answer 10

exchange of material. homologous chromosomes align and form bivalent structure

stuck together by synaptonemal complex = allows recombination (crossing over) = forms chiasma

Question 11

what are common autosomal anueploidies

Answer 11

trisomy 13 = patau’s

trisomy 18 = Edward’s

trisomy 21 = Down syndrome

Question 12

sex chromosome aneuploidies

Answer 12

turners
triple x
klinefelters
47, XXY

Question 13

describe difference of non disjunction in mitosis and meiosis

Answer 13

meiosis = affects zygote

mitosis = post zygotic, affects some cells of individual, but if in production of gametes, ALL cells are affected. most cells are 2n, some are 2n + 1 = mosaicism

Question 14

define partial trisomy/monosomy

Answer 14

full monosomy arises by non disjunction. occurs by microdeletion