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BIOC192 > Lecture 16: HOW ARE WE ALL DIFFERENT? > Flashcards

Lecture 16: HOW ARE WE ALL DIFFERENT? Flashcards

1
Q

What is Mendel’s first law?

A

Law of Segregation

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2
Q

What is the Law of Segregation?

A

When gametes form, alleles are separated so that each gamete carries only one allele for each gene

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3
Q

What is Mendel’s second law?

A

Law of Independent Assortment

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4
Q

What is the Law of Independent Assortment?

A

The segregation of alleles for one gene occurs independently to that of any other gene

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5
Q

What is Mendel’s third law?

A

Law of Dominance

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6
Q

What is the Law of Dominance?

A

Some alleles are dominant while others are recessive; an organism with at least one dominant allele will display the effect of the dominant allele

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7
Q

What is an allele?

A

An alternative form of a gene (one member of a pair) that is located at the same place on a chromosome. An allele inherited for a gene may be different from mum and dad

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8
Q

What is recombination?

A

Shuffling of DNA in chromosomes during meiosis

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9
Q

What happens first before recombination?

A

Homologous chromosomes (same genes, different DNA sequences) undergo replication to form sister chromatids (same DNA sequence)

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10
Q

What happens after homologous chromosomes replicate?

A

The homologous pairs of sister chromatids pair up and undergo recombination

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11
Q

What is the result of recombination?

A

Each gamete gets one copy of the chromosome, each with a unique combination of alleles

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12
Q

What is the exception to Mendel’s second law?

A

When two genes are close together on a chromosome - genetic linkage

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13
Q

How are genetically linked alleles inherited?

A

Often together, rarely independently

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14
Q

What is a recessive allele?

A

A version of the gene that does not encode a functional protein

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15
Q

What happens when there is a recessive mutation (Aa)?

A

When there is a mutation in either the gene from mum or dad there will be no problem as the normal copy from the other parent can mask the mutated one

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16
Q

What happens when there is a homozygous recessive mutation (aa)?

A

When both parents have the mutation for an enzyme there will be an accumulation of the precursor and no product formed (an observable effect)

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17
Q

What is the dominant allele for pea pigment?

A

Functional CHS enzyme is produced

18
Q

What is the recessive allele for pea pigment?

A

Mutation so no CHS mRNA (therefore no CHS protein)

19
Q

When is there no product?

A

If there is too recessive alleles present

20
Q

What do we inherit?

A

A unique combination of alleles from our parents

21
Q

How identical is the DNA of any two people?

A

99.4% so it differs at about 20 million places (0.6% of the total 3.2 billion base pairs)

22
Q

How many of the different base pairs in individuals might affect how our genes function?

A

5% (1 million)

23
Q

What determines how some genetic differences affect us?

A

Environment

24
Q

What causes alkaptonuria?

A

A lack of the enzyme needed to complete the final step of breaking down phenylalanine

25
Q

What is alkaptonuria?

A

Black urine caused by a genetic recessive defect meaning there is an accumulation of protein 4

26
Q

What happens if there is a defect in the first enzyme?

A

It leads to an accumulation of phenylalanine and to phenylketonuria (PKU)

27
Q

How many people does phenylketonuria affect?

A

1 in 100,000

28
Q

What happens if there is a defect in the second enzyme?

A

It leads to tyrosinemia Type 2

29
Q

How may people does tyrosinemia type 2 affect?

A

1 in 250,000

30
Q

What happens if there is a defect in enzyme 3?

A

It leads to tyrosinemea type 3

31
Q

How many people does tyrosinemai type 3 affect?

A

Very rare

32
Q

What happens if there is a defect in enzyme 4?

A

It leads to alkaptonuria

33
Q

How many people does alkaptonuria affect?

A

1 in 250,000

34
Q

What can PKU lead to?

A

Intellectual disability, seizures, behavioural problems and mental disorders because biochemistry is complex networks

35
Q

What does increased phenylalanine cause?

A

An increase/build up of phenylpyruvate and phenylethylamine which could be toxic to the brain

36
Q

What can lack of tyrosine cause?

A

A decrease in neurotransmitters (dopamine, adrenaline)

37
Q

What can phenotype be affected by?

A

Environment and genetics

38
Q

How can environment affect PKU?

A

A low phenylalanine diet prevents intellectual disability and associated problems in PKU individuals

39
Q

Where is phenylalanine transported?

A

Across the blood-brain barrier

40
Q

What does genetic variation mean (PKU)?

A

The efficiency of the transporter differs between individuals

41
Q

What do individuals with less efficient transporters have?

A

Lower levels of phenylalanine in the brain and less damage (higher IQ)

BIOC192 (38 decks)

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