genetics

Question 1

What are the 2 contributing factors to acquiring a disease?

Answer 1

genetics and environment

Question 2

Detail the structure of DNA

Answer 2

strands of DNA pair up in an antiparallel fashion
replicated and read in 5’ to 3’ direction

information held in base sequence in sugar phosphate backbone

Question 3

What are chromosomes?

Answer 3

DNA strand associated with protoeins (histones) and is wound into a chromsome

Question 4

What is the cell cycle?

When does DNA synthesis occur?

Answer 4

G1 - S - G2 - M - G1

DNA synthesis occurs in the s phase

Question 5

Detail the roles of DNA helicase, DNA polymerase, DNA ligase

Answer 5

DNA H - unwinds DNA
DNA polymerase - copies 5-3 strand and copies 3-5 strand in okazaki fragments
DNA ligase - joins the fragments together

Question 6

What is mitosis?

Answer 6

One diploid parent becomes 2 identical diploid daughter cells

Question 7

Meiosis

Answer 7

One diploid parent cell becomes 4 haploid daughter cells
crossing over occurs
gametes and formed

Question 8

What are the sequence variations within a gene?

Answer 8

changes in promoter sequence and exon sequence

Question 9

What are some sequence changes in DNA between genes?

D+D?

Answer 9

single nucleotide polymorphisms - larger deletions or duplications

Question 10

What is a polymorphism?

Answer 10

any variation in the human genome which has a population frequency of greater then 1%

does not cause disease in its own right but may predispose someone to acquiring a disease

Question 11

What is a mutation?

Answer 11

gene change that causes genetic disorder

any heritable change in the human genome

Question 12

multifactorial disease =

Answer 12

multiple polymorphisms cause risk of disease

Question 13

What is a normal female chromosome?

Answer 13

46 XX

Question 14

What is an unbalanced chromosome rearrangement?

Answer 14

Extra or missing chromosomal material

usually 1 or 3 copies of the genome

Question 15

Aneuploidy?

Answer 15

whole or extra missing chromosome

Question 16

translocation

Answer 16

Rearrangement of chromosomes

Question 17

What does 47 XY + 21 create?

Answer 17

down syndrome, trisomy 21

Question 18

47XY + 14?

Answer 18

miscarriage, trisomy 14

Question 19

47 XY + 18

Answer 19

Edward syndrome - trisomy 18

Question 20

45 X

Answer 20

turner syndrome

Question 21

47 XXY

Answer 21

klinefelter syndrome

Question 22

What is robertson translocation?

Answer 22

two acrocentric chromosomes stuck end to end, increased risk of trisomy in pregnancy

Question 23

When is microarray CGH used?

Answer 23

1st line chromosome test, detects any missing or duplicated piece of chromosome - finds polymorphisms

Question 24

What is mosaicism?

Gonadal and somatic?

Answer 24

Mosaicism occurs when a person has two or more genetically different sets of cells in his or her body. If those abnormal cells begin to outnumber the normal cells, it can lead to disease that can be traced from the cellular level to affected tissue, like skin, the brain, or other organs.

different cells have a different genetic constitution -

Gonadal:
causes recurrence risk for autosomal dominant conditions even if parent is unaffected

somatic - all cells suffer as they divide, but repair mechanisms exist

Question 25

What are tumour suppressors?

Answer 25

genes stop cells dividing if switched on

Question 26

What are oncogenes?

Answer 26

some genes start cells dividing when switched on

Question 27

What is pentrance?

Answer 27

the likelihood of having a disease ( if you have a mutation)

Question 28

What is the definition of gene expression?

Answer 28

variation in disease severity if you have the mutation

Question 29

When is aCGH used? - what does it check for?

Answer 29

1st line for paediatric referrals, checks for deletions or duplications

Question 30

How does PCR work?

Answer 30

one small piece of human DNA and amplify it

Question 31

What are the different types of mutations? Stop transcription and abnormal splicing missense? nonsense? another one that involves the bases

Answer 31

promotor and splice site sequence changes - stop transcription and cause abnormal splicing base changing causing amino acid change (missense)- change in protein sequence, may or may not reduce protein function base changing causing premature stop codon ( nonsense) insertion or deletion of bases

Question 32

What is a mendelian disorder?

Answer 32

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

Question 33

Describe some factors of autosomal dominant genes

Answer 33

disease seen in all generations, 50% risk of child being affected, same risk for males and females

Question 34

Autosomal recessive? how many generations are usually affected? what is the penetrance risk? What increases the likelihood of recessive conditions in families?

Answer 34

2 faulty copies of the gene needed to cause disease only 1 generation usually affected 1 in 4 risk of an affected child if parents are carriers increased likelihood of autosomal recessive conditions being apparent in consanguineous families

Question 35

Describe an X- linked condition

Answer 35

recessive, y chromosome irrelevant, mother carrier then 50% of daughter carrier and male affected NO MALE TO MALE TRANSITION

Question 36

X- inactivation - What happens in females?

Answer 36

cell only requires 1 working copy of X chromosome females - each cell has a random X chromosome inactivated

Question 37

What is mitochondrial DNA important for and how is it inherited?

Answer 37

mitochondrial metabolic pathways and ribosomal RNA inherited almost exclusively maternally

Question 38

What is haploinsufficiency? How do mutations affect proteins?

Answer 38

only have 1 working copy is not enough - haploinsufficiency abnormal protein interferes with normal protein mutation activates gene - gain of function mutation loss of heterozygosity

Question 39

What does DNA methylation lead to?

Answer 39

modifications of histones which repress transcription

Question 40

What is imprinting? where is it found? - what is contained in these regions?

Answer 40

differences in gene expression depending paternal or maternal inheritance specific chromosomal regions contain imprinted genes Such regions usually contain both maternally and paternally imprinted genes

Question 41

What are some symptoms of angelmann-syndrome? What chromosome is it found on?

Answer 41

neuro genetic disorder - developmental delay, intellectual disability, happy demeanour chromosome 15

Question 42

What is heteroplasmy?

Answer 42

different daughter cells contain different proportions of mutant mitochondria

Question 43

What are the characteristics gained by cells on progression to cancer?

Answer 43

increase growth signals, remove growth suppression, avoid apoptosis, achieve immortality, become invasive, make own blood supply (angiogenesis), loss of DNA spell checks, avoid immune system

Question 44

What are mechanisms of gene activation?

Answer 44

duplication of gene, activation of the gene promoter, change in amino acid sequence

Question 45

What is FISH?

Answer 45

fluorescence in situ hybridisation | light up specific bit of chromosome

Question 46

What gene causes breast cancer?

Answer 46

BRCA1 - small proportion of familial breast cancer

Question 47

What is BRCA1 gene involved with?

Answer 47

DNA strand repair

Question 48

frame-shift mutation?

Answer 48

nucleotide insertion mutation - altered transcription and translation of every codon found after the mutation.

Question 49

Can you be a carrier of an autosomal gene?

Answer 49

No such thing | Only a 50% of having a child that is affected