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Medical Cell Biology and Genetics > L17- genotype, phenotype and inheritance > Flashcards

L17- genotype, phenotype and inheritance Flashcards

1
Q

central dogma

A
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2
Q

genotype

A

our set of genes

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3
Q

phenotype

A

our traits- proteins

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4
Q

what factors influence our phenotype

A
  • e.g. Genetic disorders like CF (genetic mechanism)
  • infection (environment)
  • non commiunicable disease (genotype and environment)
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5
Q

what is a gene

A

A sequence of DNA found at a specific location within chromosomes, which codes for a protein.

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6
Q

an allele is a

A

form of a gene

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7
Q

how many genes do we have

A

25,000

  • all indiviudals have two copies of each given gene ( one maternala nd one paternal)
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8
Q
A
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9
Q

many alleles of a gene

A

within a population e.g. why we have different hair and eye colours

  • gene codes of hair colour
  • allele codes for the specific colour
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10
Q

homozygous

A

tow alleles of a gene are the same

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11
Q

heterozygous

A

two alleles of a gene are different

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12
Q

hemizygous

A

only one allele of a gene on the X chromosome (male only)

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13
Q
A
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14
Q

dominant

A

a dominant alleles in a heterozygote determines phenotype (Aa – would have A phenotype)

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15
Q

recessive

A

the non-dominant allele in a heterozygote is called recessive.

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16
Q

co- dominance

A

where both alleles have equal contribution to phenotype e.g. ABO blood types

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17
Q

co-dominance and ABO blood groups

A

Human isoglutamin gene codes for glycoproteins on the surface of RBC.

Three alleles for blood type:

  • A or I^A
  • B or I^B
  • O or I^O

We have 2 alleles each

  • Allele A is dominant over O
  • Allele B is dominant over allele O
  • Neither A or B is dominant over the other= Co-dominant
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18
Q

in a pedigree each line represents

A

a separate generation

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19
Q

oldest sibling on the pedigree will be

A

furthest to the left

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20
Q

how to draw a pedigree- reminder of symbols

A
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21
Q

describe III.17

A

youngest of 8 children, married with no children

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22
Q

in autosomal recessive disorders, heteozygotes will be

A

unaffected

23
Q

in autososmal recessive disorders males and females

A

equally affects

24
Q

in autososmal recessive disorders, if both parents are heterozygotes

A

Two heterozygotes have 25% chance of having affected offspring

25
Q

with autosomal recessive disordrrs, 2 affected homozygous individuals will have

A

affected offspring only

26
Q

heterozygous pedigree characteristic

A

isease comes out of nowhere (disease skip generations). Both parents of the affected must be heterozygous ‘carriers’ e.g. CF

27
Q

in autosomal domiannt disorders heterozygotes will be

A

affected

28
Q

in autosomal dominant disorders male and females are

A

equally affected

29
Q

autosomal domiannt disorders are rarely found

A

in homozygous state

  • if you see individual with disease, assume they are heterozygous
30
Q

every individual with autosomal dominant disorder in heterozygous form

A

has a 50% chance of haveing affected off spring

e.g. huntingtons disease

31
Q

characteristic of autosomal domiannt pedigree

A

will not skip generations

  • every affected indiivudal will have at lest one affected parent
32
Q

who are affected with X-linked recessive disorders

A

Hemizygous men and homozygous females are affected.

33
Q

X-linked recessive disorders always more common in

A

males

34
Q

heterozygous female carrier has a

A

50% chance of havign an affected son

35
Q

man with x-linekd recessive disorder cannot

A

cannot give trait to sons (only get Y chromosomes from dad)

E.g. Haemophilia

36
Q

x-linked recessive pedigree

A

Son is hemizygous recessive

Every affected male will have a heterozygous carrier mother

Every affected female will have an affected father and a carrier mother

37
Q

show an x-linked recessive punnet square example for haemophilia

A

no H gene on the Y chromosome

38
Q

in X-linked dominant disorders men and women

A

affected

  • hemizyous males
  • heterozygous females
39
Q

in x-linked dominant diseases females have a ….. chance of havign affected offspring

A

50%

40
Q

in X-linked dominant disroders, affecrted males cannot give traits to sons, but will

A

give it to all their daughters e.g. fragile X syndrome

41
Q

Y linked disorders only occur in

A

males

  • appearin all sons of males who exhibit that trait
  • absent in daughters of trait carriers (pehnotypically normal)
    e. g. male infertility
42
Q

mitochondrial inhertiance occurs due to

A

mitochodria having separate DNA (mDNA)

43
Q

mDNA is inherited from

A

mother due to sperm mitochondria not entering the egg.

44
Q

polygenic/ complex or multifactorial inheritance shows that

  • give an example
A

More than one gene can be involved in producing a phenotype

e.g. albinism

45
Q

Albinism is inherited in a recessive manner- monogenic or polygenic?

  • monogenic
A

(Albinisms is inherited in a recessive manor)

One gene: Gene A: Two alleles: A, a

You would expect all offspring to be albino…. HOWEVER in real life non of the offspring are affected.

46
Q

Albinism is inherited in a recessive manner- monogenic or polygenic?

  • polygenic
A

Two genes: Gene A1 (A1,a1) and A2 (A2, a2)

47
Q

genes on the same chromosome are said to be

A

linked

48
Q

genes on different chormsosmes are said to be

A

not linked

49
Q

linked genes do not show

A

independent assortment at meiosis

50
Q

what can occur to linked chromosomes

A

crossing over

51
Q

linked chromsosmes can show corssinging over in prophase, producing

A

new combinations of zygotes

52
Q

recombination frequency in linked chromosomes depens on

A

the distance between the two linked genes

  • Genes closely together are ‘tightly linked’
  • Genes far apart on the same chromosome behave as unlinked genes
53
Q

which linked genes are more likely to cross over

A

e. g. A and E much more likely to cross over than A and D or E and D.
- closer together

Medical Cell Biology and Genetics (33 decks)

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