Week 1: Hereditary Flashcards

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1
Q

What were the 2 theories of inheritance

A

Blending
- 2 parents mix (blend)
Particulate
- Parents pass discrete heritable units that retain identity (alleles)

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2
Q

What are the 4 rules for the law of segregation?

A
  1. Alt. versions of genes account for the variations
  2. You inherit 2 alleles (1 from each parent)
  3. If alleles differ dominant is seen
  4. two alleles separate during gamete production
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3
Q

What is the typical phenotypical ratio in dihybrids?

A

9:3:3:1

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4
Q

What is the rule of multiplication?

A

Probability of a compound event is equal to product of separate probabilities of independent single events
e.g. 1/2 x 1/2 = 1/4 (coin toss)

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5
Q

What is the rule of addition

A

probability of an event that can occur in 2 or more independent ways = sum of separate probabilities 1/4 + 1/4 = 1/2

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6
Q

Explain incomplete dominance

A

Both alleles are expressed + a combination is seen

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7
Q

Explain codominance

A

2 alleles alter phenotype in separate ways

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8
Q

What is an example of a dominant recessive relationship?

A

Tay-Sachs Disease

  • Brain cells can’t metabolise gangliosides (faulty enzyme)
  • Only homozygotes have disease (recessive)
  • Hetrozygotes have intermediate phenotype (not complete disease): half the amount of enzyme needed (incomplete dominance)
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9
Q

What is Pleiotrophy?

A

Most genes do not just affect one character/ phenotype (many symptoms) e.g. sickle cell anaemia

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10
Q

What is Epistasis?

A

More than 1 allele involved in phenotype (work together in a process) e.g. hair colour and baldness

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11
Q

What is an example of Polygenic inheritance?

A

Human skin colour (determined by 3 genes)

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