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Heredity And Genetics Flashcards

1
Q

What is a gene?

A

A gene is a unit of inheritance found on chromosomes that controls specific characteristics in an organism.

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2
Q

What is an allele?

A

An allele is a different form of a gene found at the same place on homologous chromosomes.

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3
Q

Define genotype.

A

Genotype is the genetic makeup of an organism—the combination of alleles it possesses.

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4
Q

Define phenotype.

A

Phenotype is the observable characteristics of an organism, resulting from its genotype and environment.

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5
Q

What does homozygous mean?

A

An organism is homozygous when it has two identical alleles for a particular gene.

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6
Q

What does heterozygous mean?

A

An organism is heterozygous when it has two different alleles for a particular gene.

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7
Q

What is a dominant allele?

A

A dominant allele is one that is expressed in the phenotype even if only one copy is present.

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8
Q

What is a recessive allele?

A

A recessive allele is expressed in the phenotype only when two copies are present.

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9
Q

What is a genetic diagram?

A

A genetic diagram shows a cross between two genotypes and predicts offspring genotypes and phenotypes.

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10
Q

What is codominance?

A

In codominance, both alleles are equally expressed in the heterozygous individual without blending.

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11
Q

What are examples of codominance in humans?

A

Human ABO blood groups, where alleles IA and IB are codominant.

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11
Q

What is incomplete dominance?

A

In incomplete dominance, the heterozygous phenotype is a blend of both alleles, as neither is completely dominant.

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12
Q

What determines blood groups in humans?

A

Blood groups are determined by three alleles: IA, IB, and IO

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13
Q

What are the possible phenotypes for blood groups with the alleles IA, IB, and IO?

A

A, B, AB, and O.

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14
Q

How is sex determined in humans?

A

Sex is determined by one of the 23 pair of chromosomesin the human cell : XX for female, XY for male.

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15
Q

What are sex-linked characteristics?

A

Traits controlled by genes located on the sex chromosomes, especially the X chromosome.

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16
Q

Why are sex-linked traits more common in males?

A

Males have only one X chromosome, so a recessive allele on it will be expressed without a second X to mask it.

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17
Q

What is haemophilia?

A

A sex-linked disorder where the blood does not clot properly due to a recessive allele on the X chromosome.

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18
Q

Can females be carriers of haemophilia?

A

Yes, if they have one normal allele (XH) and one haemophilia allele (Xh), they are carriers.

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19
Q

What causes sickle cell anaemia?

A

A recessive allele, HbS, that causes red blood cells to take a sickle shape instead of the normal biconcave shape.

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19
Q

What is the genotype of someone with sickle cell disease?

A

HbSS - all red blood cells take the sickle shape, the person has sickle cell anaemia

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20
Q

What is the genotype of someone with sickle cell trait?

A

HbNS – they are carriers and may have some sickled red blood cells. (30-40%)

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21
Q

What is the genotype of a normal individual for the sickle cell gene?

22
Q

What is variation?

A

Differences between individuals of the same species, caused by genetic and environmental factors.

23
What is continuous variation?
Variation that shows a range of values (e.g., height, skin color).
24
What is discontinuous variation?
Variation with distinct categories (e.g., blood group, tongue rolling).
25
What are homologous chromosomes?
Chromosome pairs that carry the same genes but may have different alleles.
26
How many chromosomes are found in a human body cell?
46 chromosomes, or 23 pairs.
27
What does a genetic cross between BB and bb produce?
All Bb offspring (heterozygous) with the dominant trait expressed.
28
What is a pedigree chart?
A diagram that shows how a trait is inherited through generations in a family.
29
How do genotype and environment interact?
The genotype provides potential traits, but environmental factors like diet or lifestyle can influence how traits are expressed (e.g., in identical twins).
30
What type of graph is used to show continuous variation?
A histogram is used to show continuous variation. This is because the data forms a smooth curve or bell shape, showing a gradual range of differences (e.g., height, weight).
31
What type of graph is used to show discontinuous variation?
A bar chart is used to show discontinuous variation, as the data falls into separate, distinct categories (e.g., blood type, ability to roll tongue).
32
Give three examples of discontinuous variation.
Blood group Ability to roll the tongue Presence or absence of albinism
33
Give three examples of continuous variation.
Height Weight Skin color
34
What is a genetic disorder?
A genetic disorder is a disease or condition caused by a mutation in one or more genes. These disorders are inherited from parents and can cause harmful traits.
35
Why is albinism considered a genetic disorder?
Albinism is considered a genetic disorder because it is caused by a mutation in a gene responsible for melanin production. It is passed on through inherited recessive alleles.
36
How is albinism inherited?
Albinism is inherited in a recessive pattern. This means a person must receive the faulty gene from both parents to express the condition.
36
What are the characteristics of someone with albinism?
People with albinism have very light or white hair, pale skin, and pink or light blue eyes. They may also suffer from vision problems and sun sensitivity due to lack of melanin.
37
Can the environment affect whether a person has albinism?
No. Albinism is purely genetic. The environment does not influence whether a person has albinism or not.
38
Which type of variation does albinism represent and why?
Albinism is an example of discontinuous variation because it is a clear, yes-or-no condition — you either have it or you don't.
39
What is the difference between inherited and environmental variation?
Inherited variation is passed on from parents through genes (e.g., blood type). Environmental variation is caused by lifestyle and surroundings (e.g., scars or accent).
40
How does mutation contribute to variation?
Mutations are random changes in DNA that create new alleles, increasing genetic variation within a population.
41
Can mutations be inherited?
Yes. If a mutation occurs in reproductive cells (gametes), it can be passed on to offspring and affect future generations.
42
Why is it important to study variation?
Studying variation helps us understand how traits are passed on, how populations evolve, and how we can treat or prevent genetic disorders.
43
What is red-green colour blindness?
Red-green colour blindness is a condition where a person mixes up all colours that include red or green. For example, they may confuse blue and purple (since purple contains red) because they cannot perceive the red part of the colour.
44
What causes red-green colour blindness genetically?
It is caused by a recessive gene (n) on the X chromosome. The normal gene is represented as N, which is dominant.
45
What is the genotype notation for red-green colour blindness?
N = dominant normal vision gene n = recessive gene for red-green colour blindness
46
Who is more likely to inherit red-green colour blindness and why?
Males are more likely because they have only one X chromosome. If they inherit the n gene, they will be colour blind since there is no second X to carry a normal N gene.
47
What is a chromosomal mutation?
A chromosomal mutation is when the entire chromosome is affected, not just a gene. This can result in conditions like Down's syndrome.
48
What causes Down's syndrome?
Down’s syndrome is caused when the zygote receives an extra chromosome, specifically on chromosome #21. This is called trisomy 21.
49
What are the characteristics of a person with Down's syndrome?
A person with Down’s syndrome may have: Mental retardation Short arms and legs Internal defects Abnormal facial traits
50
When is Down’s syndrome more likely to occur?
It is more likely when the mother is older, especially over 40 years of age.
51
What is albinism?
Albinism is a genetic condition where the body does not produce melanin, the pigment responsible for skin, hair, and eye colour.
52
What are the physical characteristics of a person with albinism?
A person with albinism usually has: Very light or white hair Pale skin Light blue or pinkish eyes Little or no colour in their hair, skin, and eyes
53
What is melanin and what is its function?
Melanin is a natural black pigment in the body that gives colour to the skin, hair, and iris of the eyes. It also protects the skin from UV radiation.

Biology (22 decks)

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