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Alex's Genetics > Lecture 9b > Flashcards

Lecture 9b Flashcards

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Biology 101 flashcards
1
Q

What is Simple Mendelian inheritance? Is it often like this?

A

A single gene with two different alleles, forming a simple dominant/recessive relationship.

Mendel got lucky because it is often not like this.

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2
Q

Around how many mendelian (single gene) diseases are there? How easy is it to detect these disease genes?

A

About 4,000.

It is easy to find the disease genes.

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3
Q

What are 3 things that can influence the severity of a mendelian disease?

A

1) Genetic background
2) Epigenetics
3) Environment

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4
Q

What are pedigrees?

A

Family trees that give us information on human traits from generation to generation.

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5
Q

What does pedigree analysis allow for?

A

Allows us to determine the pattern of inheritance of human traits.

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6
Q

Just know this

A

You idiot

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7
Q

What are most types of diseases?

A

Autosomal Recessive Disease.

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8
Q

What type of disease has this pedigree?

A

Autosomal recessive diseases. Tay-Sachs is an example of an autosomal recessive disease.

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9
Q

Describe autosomal recessive disease.

A

To get it, you need to receive the recessive allele from both your mother and father. If you receive just one, you are just a carrier.

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10
Q

How common are dominant mutation diseases?

A

A MINORITY of human diseases are caused by dominant mutations.

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11
Q

Describe dominant mutations.

A

Cause a DOMINANT PATTERN of inheritance. Everyone who has an allele with the mutation has the disease.

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12
Q

What type of disease is this showing? What is an example of this type of disease?

A

Autosomal dominant disease. Huntington’s disease is an example of this.

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13
Q

What are 3 common explanations for dominant disorders?

A

Haploinsufficiency, gain-of-function mutations, and dominant negative mutations.

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14
Q

What is haploinsufficiency?

A

One allele does not make enough product to function normally.

In other words, the heterozygote has 50% of the normal protein and this is not sufficient for a normal phenotype.

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15
Q

What are gain-of-function mutations?

A

A mutation changes proteins so that it gains a new function.

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16
Q

What are dominant negative mutations?

A

An altered gene product will act antagonistically to the normal product.

A bad polypeptide could poison the good polypeptide, making the protein non-functional.

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17
Q

What do we, as geneticists, know about autosomal dominant diseases?

A

In many cases, we have cloned and mapped the mutant genes responsible for these diseases.

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18
Q

T/F: Almost all disease genes have been found for autosomal dominant diseases.

A

True! Numerous genetic diseases are inherited as autosomal dominants.

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19
Q

What is an example of a gain-of-function mutation?

A

Ras is a protein that promotes cell division. In 20% of human cancer tumors, Ras is mutated so that it is constantly active, thus, it is dividing all the time, which causes a benign tumor. This is one step closer to cancer.

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20
Q

What is an example of a dominant negative mutation?

A

p53 is a protein that prevents cancer. Most p53 proteins are simple loss-of-function (both alleles are deleted). However, these proteins act as a tetramer to prevent cancer. In >50% of human cancer tumors, p53 is mutated to make proteins that will poison the tetramer, making it non-functional. This stops the tetramer from preventing cancer.

21
Q

What does a pedigree typically look like for X-linked genes?

A

Mostly males are affected with their mothers acting as carriers. This is because males only have 1 copy of the X chromosome, so if their mother is a carrier, they have a 50% chance of getting the disease.

22
Q

In X-linked genes, why do we not generally see affected females?

A

Affected males generally do not have children. However, if they did, an affected male would have to mate with a carrier female to even have a possibility of having an affected female.

23
Q

What differs between male and females relative to their chromosomes?

A

Many species have males and females that differ in their sex chromosome composition. This means that certain traits are governed by genes on the sex chromosomes.

24
Q

What type of disease is this?

A

X-linked genes

25
Q

What is an example of an X-linked recessive disease?

A

Hemophilia

26
Q

What is incomplete dominance?

A

The heterozygote exhibits a phenotype that is intermediate between the corresponding homozygotes. It is like there is a BLENDING of the two parents.

27
Q

What is incomplete dominance called if it causes disease?

A

Haploinsufficiency

28
Q

What is this showing?

A

Incomplete dominance

29
Q

What is incomplete penetrance?

A

An allele is dominant in some heterozygous individuals but not in others.

30
Q

What type of disease is Polydactyly?

A

Heterozygous disease. This means that a single copy of the polydactyly allele is usually sufficient to cause this condition.

31
Q

What is Polydactyly?

A

Affected individuals with an autosomal dominant trait have additional fingers and/or toes.

32
Q

T/F: All individuals carrying the dominant polydactyly allele exhibit the trait.

A

False! There can be individuals carrying the dominant mutant allele but not exhibiting the trait.

33
Q

What level is the measure of penetrance described at?

A

The population level

34
Q

If 60% of heterozygotes carrying a dominant allele exhibit the allele’s trait, how penetrant is the trait?

A

The trait is 60% penetrant.

This is like saying how effective is the trait at showing when it is carried.

35
Q

What do we attribute the range of phenotypes in incomplete penetrance to be due to?

A

Environment and/or other genes.

36
Q

What is this pedigree showing?

A

Incomplete penetrance

37
Q

When we look at phenotypes in the environment, what do we notice?

A

Environmental conditions have a great impact on the phenotype of an individual. Phenotypes can switch due to the environment.

38
Q

What is an example of how phenotypes are influenced by the environment?

A

The arctic fox changes coat color from grayish brown in the summer to white in the winter.

39
Q

What are antibodies?

A

Proteins produced by the immune system that bind to foreign things in the body.

40
Q

When antibodies bind, what does this signal?

A

Binding of antibodies signals white blood cells to gobble up the foreign thing.

41
Q

Relative to antibodies, what occurs during early development?

A

When we are first developing, we make antibodies for all sorts of random specificities, including antibodies that never recognize anything.

42
Q

Relative to antibodies, what happens as we develop?

A

As we grow and develop, the body gets rid of all cells that produce antibodies recognizing human antigens (things in our body we want).

43
Q

What is codominance? What is an example of this?

A

Neither allele dominates over the other, so both alleles are expressed in a heterozygous individual.

Blood groups are an example of multiple alleles with codominance.

44
Q

How do we determine blood group?

A

Blood group is determined by the type of antigen present on the surface of red blood cells.

45
Q

What are the 3 different types of antigens found on red blood? What alleles are each controlled by?

A

Antigen A, which is controlled by allele IA

Antigen B, which is controlled by allele IB

Antigen O, which is controlled by allele i

46
Q

When we see allele i, what does this mean regarding sugar?

A

There is no sugar attached. This is what we call the Universal Donor.

47
Q

T/F: Allele i is dominant to both IA and IB.

A

False. Allele i is recessive to both IA and IB.

48
Q

What alleles are codominant?

A

IA and IB are codominant when they are together.

This is type AB blood.

49
Q

Memorize this. This is ABO blood group inheritance pattern.

A

Dumbass

Alex's Genetics (38 decks)

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