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Biology 2 > 9. Patterns of Inheritance > Flashcards

9. Patterns of Inheritance Flashcards

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1
Q

What is monogenic inheritance?

A

The basic inheritance of a single gene

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2
Q

What are alleles?

A

Different versions of the same gene

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3
Q

What are the two types of alleles?

A

Dominant- are always expressed when they are present.

Recessive- are only expressed in homozygous recessive genes.

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4
Q

What is Heterozygous?

A

When there are both dominant and recessive alleles present.

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5
Q

What is Homozygous?

A

Either both dominant or both recessive alleles present.

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6
Q

Who was Gregor Mendel?

A

He is considered the father of genetics.

His research on pea plants allowed him to come up with The Law of Segregation and The Law of Independent Assortment.

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7
Q

What was The Law of Segregation?

A

Established that there are dominant and recessive traits passed on randomly from parents to offspring.

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8
Q

What was the Law of Independent Assortment?

A

Established that traits were passed on independently of other traits from parent to offspring.

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9
Q

Why did Mendel use pea plants in his research?

A

They were easy to grow, could be bred rapidly, and had several observable characteristics, like petal colour, pea colour, Stem height and pod shape.
These genes were monogenic- determined by one gene.

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10
Q

What is codominance?

A

When both alleles in the inherited gene are expressed in the phenotype.

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11
Q

Where is codominance found?

A

Roan cattle
MN blood group
ABO blood group
Sickle cell anaemia (sickle cell trait)

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12
Q

How does codominance work in shorthorn cattle?

A 
The gene for coat colour has two alleles
CR (red) and CW (white)
Homozygous red- Red coat
Homozygous white- White
Heterozygous- roan coat
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13
Q

How does codominance work in MN blood groups?

A

Controlled by a single gene with two alleles, Gm and Gn.
Each gene codes for a different protein on the surface of erythrocytes.
These alleles are codominant.

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14
Q

How does codominance work in ABO blood groups?

A

Controlled by three alleles.
Ia, Ib are codominant.
Io is recessive.
This means there are six possible genotypes.

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15
Q

What causes sickle cell anaemia?

A

A mutation in the gene that codes for the β-globin chain of haemoglobin.

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16
Q

What is sickle cell anemia?

A

Red Blood cells, which usually have a biconcave shape, have a sickle (crescent) shape.
This causes them to clump together and clog capillaries.

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17
Q

What is the normal and mutant allele which causes sickle cell anaemia?

A

Mutant allele- Hbs
Normal allele- Hbn
Heterozygous people do not suffer from sickle cell anaemia.

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18
Q

Where is codominance present in sickle cell anemia

A

Alleles are considered codominant when the type of haemoglobin is the phenotype.
However, when sickle cell anaemia is the phenotype, codominance is not present, Hbs is recessive.

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19
Q

How is Hbs recessive at an organism level?

A

A heterozygous genotype means they do not have sickle cell anaemia but do have some sickle cells.

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20
Q

What is sickle cell trait (SCT)?

A

Carriers that do not suffer the symptoms of SCD.

21
Q

What are the benefits of sickle cell trait?

A

They have protection against malaria.

Plasmodium protists cannot spread in the red blood cells of those with SCT.

22
Q

What is the genotype of someone with sickle cell trait?

A

Hbs Hbn

23
Q

What is the genotype of a non-sufferer of sickle cell?

A

Hbn Hbn

24
Q

What is the genotype of someone with sickle cell disease?

A

Hbs Hbs

25
Q

What are sex chromosomes?

A

One of the 23 pairs of chromosomes that determines sex.

Each pair is called a ‘linkage group’ and will be inherited together.

26
Q

Which genes are described as ‘sex linked’?

A

Genes found on the non-homologous region of the X chromosome.

27
Q

What is Haemophilia A?

A

Prevents the blood from clotting fast enough- bleeding can cause bleeding or a haemorrhage.

28
Q

What causes haemophilia A?

A

It is sex linked.
Genes on a region of the X chromosome code for the blood-clotting factor 8.
A mutated form of the allele codes for non-functioning factor 8.

29
Q

How is a female with a mutated allele on one X chromosome impacted by haemophilia?

A

They produce enough functioning factor 8 to enable blood clotting- they are a carrier.

30
Q

How is a male with an mutated haemophilia allele on his X chromosome impacted by haemophilia?

A

He will suffer from haemophilia A.

31
Q

What causes red-green colour blindness?

A

It is sex linked.
Caused by a recessive c on the X chromosome.
If someone has colour-blindness their genotype is…
Male- Xc and Y
Female- Xc and Xc

32
Q

Where is sex linkage present in cats?

A

One of the genes for coat colour is sex-linked.
The allele CO produces orange fur.
The allele CB produces black fur.
These alleles are codominant.
Genotype XCO and XCB have patches of black and yellow fur (tortoiseshell).

33
Q

What is linkage?

A

When two or more genes are located on the same chromosome.
They will not be separated during independent assortment.
They are inherited together.

34
Q

What is autosomal linkage?

A

When genes are linked by being on the same autosome.

35
Q

What is an autosome?

A

Chromosomes that are not the sex chromosomes.

36
Q

How does autosomal linkage impact the phenotype ratio?

A

Means that more offspring will have the same genotype and phenotype of their parents.
Unless the genes are separated during crossing over.

37
Q

How does the positioning of loci on a chromosome impact inheritance?

A

The closer the loci of two genes on an autosome the more closely linked they are.
They are more likely to be inherited together,

38
Q

What is dihybrid inheritance?

A

The simultaneous inheritance of two genes that are not linked.

39
Q

What is the chi-squared test?

A

Compares observed results with expected results.

Designed to find out if the difference between the two is statistically significant.

40
Q

When can the chi-squared test be used?

A

The raw data is in categories.
We have a strong theory to use to predict values.
The sample size is large.

41
Q

What is the null hypothesis?

A

There is no statistically significant difference between the observed and expected data.
Any difference is due to chance.

42
Q

How do you calculate the chi-squared value?

A
  1. Place the values given into the given chi-squared equation.
  2. Calculate the degree of freedom (number of values minus 1).
  3. Cross-reference the degree of freedom with the value of 0.05.
  4. If your calculated value is lower than the value in the table, you accept the null hypothesis.
43
Q

What factors can affect allele frequencies within populations?

A 
Population size
Mutation rate
Migration
Natural selection 
Genetic drift
44
Q

What are two examples of genetic drift?

A

Bottle neck and Founder effect.

45
Q

What is the founder effect?

A

Isolation of a population from other populations of the same species.

46
Q

What is the Hardy-Weinberg principle?

A

States that the frequency of a particular allele in a gene pool will not change from one generation to the next.

47
Q

In this equation…
p+q= 1
p^2+2pq+q^2=1
What does each letter and number represent?

A 
p= frequency of the dominant allele within a population
q= frequency of recessive allele within a population
p^2= homozygous dominant
q^2= homozygous recessive
2pq= heterozygous
48
Q

What is bottle neck?

A

When a chance event cuts off a large part of the population.

The range of alleles will likely reduce, so there is lower genetic variation.

Biology 2 (12 decks)

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