IMMS

Question 1

what is the structure of DNA?

Answer 1

double helix
comp. base pairs A-T, C-G
coils around nucleosomes, into supercoils, into chromosomes

Question 2

how Many chromosomes are in the human genome

Answer 2

46- 22 pairs + sex chromosomes, XY male XX female

Question 3

karyotype

Answer 3

number and appearance of chromosomes in cell
each chromsome= roughly 10 to 7 base pairs and several hundred genes

Question 4

arms of chromosomes

Answer 4

long arm - q
short arm- p

separated by centromere

Question 5

telomeres

Answer 5

ends of chromosome- stop them unravelling
shorten over time

Question 6

what is mitosis for

Answer 6

produces 2 identical daughter cells
- growth
- replacing dead cells

Question 7

what stage must cell be in for mitosis to occur

Answer 7

interphase - longest stage
- cell growth, DNA replicates (s phase), prepares for cell division

Question 8

Prophase

Answer 8

chromatin condenses into chromosomes
centrosomes nucleate microtubules + move to opposite ends of nucleus

Question 9

Prometaphase

Answer 9

-nuclear membrane breaks down
-microtubules invade nuclear space
- chromatids attach to microtubules

Question 10

Metaphase

Answer 10

chromosomes line up along equatorial plane

Question 11

anaphase

Answer 11

sister chromatids separate + pushed to opp. poles of cells- spindle fibres contract

Question 12

telophase

Answer 12

nuclear membrane reforms
chromosomes unfold into chromatin
cytokinesis begins

Question 13

pneumonic for mitosis

Answer 13

I prefer milk and tea:

I- interphase
p- prophase
m- metaphase
a- anaphase
t- telophase

Question 14

cytokinesis

Answer 14

cell divides into 2 daughter cells, nucleus and 46 chromosomes in each

Question 15

malignant

Answer 15

too many mitotic figures- lots of dark nuclei w. diff. sizes on histological plate

more mitotic figures= more malignant

Question 16

meiosis

Answer 16

Only in gametes

Recombination of genetic material generates diversity

Two cell divisions
4 haploid daughter cells

Question 17

meiosis 1

Answer 17

prophase 1- crossing over between non-sister chromatids

metaphase 1- random assortment occurs on equatorial line

both result in genetic diversity

Question 18

meiosis 2

Answer 18

sister chromatids separate
haploid cells produced

Question 19

sperm production

Answer 19

Primordial germ cells → lots of mitoses →Spermatogonia

Meiotic divisions commence at puberty

The cytoplasm divides evenly
After meiosis II four equal gametes

Question 20

how many sperm in ejaculation

Answer 20

process of sperm production takes 60-65 days

100/200 million sperms/ejaculatiom

Question 21

Egg production

Answer 21

Primordial germ cell → 30 mitoses → oogonia

Oogonia enter prophase of meiosis I by 8th month of intrauterine life

Process suspended

Cells enter ovulation 10-50 years later

Cytoplasm divides unequally – 1 egg and 3 polar bodies (that apoptose)

Question 22

when are meiosis 1 and meiosis 2 complete

Answer 22

meiosis 1 completed at ovulation

meiosis 2 only completed if fertilisation occurs

Question 23

Non-disjunction

Answer 23

failure of chromosome pairs to separate in meiosis 1
or
failure of sister chromatids to separate properly in meiosis 2

• can result in downs syndrome
• and turners syndrome, only 1 X chromosome

Question 24

gonadal mosaicism

Answer 24

Occurs when precursor germline cells to ova or spermatozoa are a mixture of two or more genetically different cell lines- due to errors in mitosis

likelihood increases with age

parent= healthy
fetus= may have genetic disease

most commonly autosomal dominant + X linked

Question 25

autosomal

Answer 25

chromosomes 1-22, all except sex chromosomes

Question 26

locus

Answer 26

position of gene/DNA on genetic map

Question 27

genotype

Answer 27

genetic constitution of individual

Question 28

phenotype

Answer 28

appearance of individual resulting from genotype and interaction with enviroment

Question 29

allele

Answer 29

one or several alternative forms of a gene at a specific locus

Question 30

numerical chromosome abnormalities

Answer 30

Numerical Trisomy 47,XX,+21 Monosomy 45,X Polyploidy 69,XXY

Question 31

structural chromosome abnormalities

Answer 31

translocation inversion duplication deletion

Question 32

constitutional abnormalities

Answer 32

-occur at gametogenesis -affects all cells of body - heritable

Question 33

acquired abnormalities

Answer 33

-changes occur during lifetime -restricted to malignant tissue -not heritable

Question 34

polymorphism

Answer 34

frequent hereditary variations at same locus, not mutations- can make you more or less susceptible to disease

Question 35

autozygosity

Answer 35

homozygous by descent- i.e inheritance of same mutant allele

Question 36

homozygous

Answer 36

both alleles same at locus

Question 37

heterozygous

Answer 37

diff. alleles at same locus

Question 38

hemizygous

Answer 38

genes carried on unpaired chromosome- e.g X chromosome in male

Question 39

penetrance

Answer 39

proportion of people with genotype that show expected phenotype complete- gene expressed in whole population incomplete- gene only expressed in part of population

Question 40

variable expression

Answer 40

variation in expression between individuals of clinical features of same genetic disorder

Question 41

multifactorial dominant

Answer 41

disease due to combo of genetic and environmental factors - relatives of opp. sex more likely to be affected via inheritance e.g male has the condition- female relatives are more risk