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genetics Flashcards

1
Q

What are the 2 contributing factors to acquiring a disease?

A

genetics and environment

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2
Q

Detail the structure of DNA

A

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

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3
Q

What are chromosomes?

A

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

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4
Q

What is the cell cycle?

When does DNA synthesis occur?

A

G1 - S - G2 - M - G1

DNA synthesis occurs in the s phase

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5
Q

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

A

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

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6
Q

What is mitosis?

A

One diploid parent becomes 2 identical diploid daughter cells

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7
Q

Meiosis

A

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

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8
Q

What are the sequence variations within a gene?

A

changes in promoter sequence and exon sequence

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9
Q

What are some sequence changes in DNA between genes?

D+D?

A

single nucleotide polymorphisms - larger deletions or duplications

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10
Q

What is a polymorphism?

A

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

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11
Q

What is a mutation?

A

gene change that causes genetic disorder

any heritable change in the human genome

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12
Q

multifactorial disease =

A

multiple polymorphisms cause risk of disease

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13
Q

What is a normal female chromosome?

A

46 XX

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14
Q

What is an unbalanced chromosome rearrangement?

A

Extra or missing chromosomal material

usually 1 or 3 copies of the genome

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15
Q

Aneuploidy?

A

whole or extra missing chromosome

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16
Q

translocation

A

Rearrangement of chromosomes

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17
Q

What does 47 XY + 21 create?

A

down syndrome, trisomy 21

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18
Q

47XY + 14?

A

miscarriage, trisomy 14

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19
Q

47 XY + 18

A

Edward syndrome - trisomy 18

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20
Q

45 X

A

turner syndrome

21
Q

47 XXY

A

klinefelter syndrome

22
Q

What is robertson translocation?

A

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

23
Q

When is microarray CGH used?

A

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

24
Q

What is mosaicism?

Gonadal and somatic?

A

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

25
Q

What are tumour suppressors?

A

genes stop cells dividing if switched on

26
Q

What are oncogenes?

A

some genes start cells dividing when switched on

27
Q

What is pentrance?

A

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

28
Q

What is the definition of gene expression?

A

variation in disease severity if you have the mutation

29
Q

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

A

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

30
Q

How does PCR work?

A

one small piece of human DNA and amplify it

31
Q

What are the different types of mutations?

Stop transcription and abnormal splicing

missense?
nonsense?

another one that involves the bases

A

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

32
Q

What is a mendelian disorder?

A

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

33
Q

Describe some factors of autosomal dominant genes

A

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

34
Q

Autosomal recessive?

how many generations are usually affected?

what is the penetrance risk?

What increases the likelihood of recessive conditions in families?

A

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

35
Q

Describe an X- linked condition

A

recessive, y chromosome irrelevant, mother carrier then 50% of daughter carrier and male affected

NO MALE TO MALE TRANSITION

36
Q

X- inactivation -

What happens in females?

A

cell only requires 1 working copy of X chromosome

females - each cell has a random X chromosome inactivated

37
Q

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

A

mitochondrial metabolic pathways and ribosomal RNA

inherited almost exclusively maternally

38
Q

What is haploinsufficiency?

How do mutations affect proteins?

A

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

39
Q

What does DNA methylation lead to?

A

modifications of histones which repress transcription

40
Q

What is imprinting?

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

A

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

41
Q

What are some symptoms of angelmann-syndrome?

What chromosome is it found on?

A

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

chromosome 15

42
Q

What is heteroplasmy?

A

different daughter cells contain different proportions of mutant mitochondria

43
Q

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

A

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

44
Q

What are mechanisms of gene activation?

A

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

45
Q

What is FISH?

A

fluorescence in situ hybridisation

light up specific bit of chromosome

46
Q

What gene causes breast cancer?

A

BRCA1 - small proportion of familial breast cancer

47
Q

What is BRCA1 gene involved with?

A

DNA strand repair

48
Q

frame-shift mutation?

A

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

49
Q

Can you be a carrier of an autosomal gene?

A

No such thing

Only a 50% of having a child that is affected

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