Genetics

Question 1

what are the stages of the cell cycle and when does DNA replication occur

Answer 1

G1-S-G2-M

DNA replication occurs in S phase

Question 2

what is mitosis

Answer 2

when one diploid parent forms 2 identical diploid daughter cells

Question 3

what is meiosis

Answer 3

when one diploid parent forms 4 different haploid cells.

Question 4

how does meiosis create genetically different cells

Answer 4

due to crossing over of the chromosomes

- essential for gamete formation

Question 5

how does RNA differ from DNA

Answer 5

• single stranded
• uracil instead of thymine
• ribose sugar

Question 6

what do sequence variations within a gene cause

Answer 6

changes in promotor/exon sequences

Question 7

what do sequence variations in-between genes cause

Answer 7

• SNPs (single nucleotide polymorphisms)

- larger deletions/duplications

Question 8

define polymorphisms

Answer 8

a sequence variation with a population frequency of >1%

Question 9

do polymorphisms directly cause disease

Answer 9

NO. they do not cause disease in their own right but may predispose to common diseases

Question 10

what is a mutation

Answer 10

a sequence variation that directly causes disease or any heritable change in human genome

Question 11

define a classical genetic disease

Answer 11

one mutation sufficient to cause disease

Question 12

define a multifactorial genetic disease

Answer 12

multiple polymorphisms cause risk of disease

Question 13

normal female chromosome arrangement is…

Answer 13

46XX

Question 14

what is a balanced chromosome arrangement

Answer 14

all chromosome material is present

Question 15

what is an unbalanced chromosome arrangement

Answer 15

when there is missing or extra chromosome material

Question 16

define aneuploidy

Answer 16

whole extra or missing chromosome

Question 17

what is 47XY + 21

Answer 17

downs syndrome

Question 18

what is 47XY + 14

Answer 18

miscarriage

Question 19

what is 47XY + 18

Answer 19

Edward’s syndrome

Question 20

what is 45X

Answer 20

Turner’s syndrome

Question 21

what is 47XXY

Answer 21

Klinefelter syndrome

Question 22

what is Robertsonain translocation

Answer 22

when two acrocentric chromosomes stick end-to-end

- increases risk of miscarriage

Question 23

what are acrocentric chromosomes

Answer 23

only have q arms. (long arms on bottom)

Question 24

what is microarray CGH

Answer 24

1st line chromosome test as picks up polymorphisms, deletions, duplications

Question 25

define mosaicism

Answer 25

different cells have different genetic make-up

Question 26

what is somatic mosaicism

Answer 26

all cells suffer mutations as they divide

Question 27

what genes are involved in cancer

Answer 27

oncogenes and tumour suppressors

Question 28

define penetrance of mutation

Answer 28

likelihood of getting disease if you have the mutation

Question 29

what does PCR allow you to do

Answer 29

select part of genome and amplify it

Question 30

what is a mendelian disorder

Answer 30

a disease that is caused by a change in a single gene

Question 31

what are the 3 mendelian disorders

Answer 31

- Autosomal Dominant - Autosomal Recessive - X-linked (recessive)

Question 32

What is autosomal dominant

Answer 32

- disease seen in all generations | - 50% risk of child being affected if parent is

Question 33

what is autosomal recessive

Answer 33

- 2 faulty copies of gene required to cause disease - often only one generation affected - 25% risk of child being affected if parent is

Question 34

what is X-linked (recessive)

Answer 34

- females need 2 copies to be affected - males need 1 copy to be affected - no male-to-male transmission

Question 35

what is X-inactivation

Answer 35

a cell only needs one working copy of X chromosome. In females, each cell has a random X chromosome inactivated

Question 36

what does mitochondrial DNA contain

Answer 36

genes for mitochondrial metabolic pathways and ribosomal RNA

Question 37

is mitochondrial DNA mainly maternal or paternal?

Answer 37

Maternal

Question 38

how do mutations cause disease

Answer 38

- haploinsufficiency - dominant negative (abnormal protein interferes with normal protein) - loss of heterozygosity - mutation activates gene

Question 39

what is non-mendelian inheritance

Answer 39

DNA methylation leads to modification of histones which represses transcription

Question 40

what are the non-mendelian disorders

Answer 40

imprinting, angelman syndrome, heteroplasmy

Question 41

what is imprinting

Answer 41

differences in gene expression depending on whether gene is maternally or paternally inherited - specific regions of chromosomes have imprinted genes (regions have both maternally and paternally imprinted genes)

Question 42

what is Angelman syndrome

Answer 42

- a neuro-genetic disorder - causes developmental delay - causes intellectual disability

Question 43

what is heteroplasmy

Answer 43

different daughter cells contain different proportions of mutant mitochondria

Question 44

what are the characteristics gained by cells on progression to cancer

Answer 44

- proliferation - evasion of immune system - avoid apoptosis - acquire vascular supply - metastasis

Question 45

what does FISH stand for and what is it

Answer 45

- fluorescence in-situ hybridisation | - light up specific bit of chromosome

Question 46

breast cancer mutations

Answer 46

BRCA1

Question 47

what are the rare autosomal cancers

Answer 47

- young age onset - many cancers - rare tumours

Question 48

what are the multifactorial predispositions of cancer

Answer 48

- everyone at some risk | - anyone with family history