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UACE Biology > Inheritance And Evolution > Flashcards

Inheritance And Evolution Flashcards

1
Q

Define variation

A

Differences in characteristics among organisms of the same natural population or species

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2
Q

What is continuous variation and its characteristics?

A

Type of variation in which individuals show a complete gradation from one extreme to the other without any break.

  • Has intermediates
  • Caused by both environmental conditions and genetic factors
  • They are quantitative and can be measured eg height, weight
  • They are polygenic (controlled by many genes)
  • Gives a normal distribution curve with many organisms lying in the normal
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3
Q

What is discontinuous variation and its characteristics?

A

Type of variation in which individuals show clear-cut differences with no intermediates between them

  • Has no intermediates
  • Caused by genetic factors
  • They are qualitative and cannot be measured
  • They are controlled by a single gene
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4
Q

Give examples of continuous and discontinuous variation

A

Continuous;
- Skin color
- Height
- Intelligence
- Weight
- Length

Discontinuous;
- Blood types in humans
- Wing lengths in drosophila
- Sex in humans

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5
Q

What is a gene?

A

A basic unit of inheritance for a given characteristic

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6
Q

What is a phenotype?

A

The outward appearance of an organism

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7
Q

What is a genotype?

A

The genetic constitution of an organism with respect to the alleles

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8
Q

What is an allele?

A

One of a number of alternative forms of the same gene responsible for determining contrasting characteristics

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9
Q

Distinguish between homozygous and heterozygous

A

Homozygous is a diploid condition in which alleles at a given locus are identical while heterozygous is a diploid condition in which alleles at a given locus are different

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10
Q

What is the dominant allele?

A

An allele, which influences the appearance of the phenotype, even in the presence of an alternative allele

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11
Q

What is the recessive allele?

A

An allele, which influences the appearance of the phenotype only in the presence of another identical allele.

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12
Q

Give examples of characteristics that follow monohybrid inheritance

A
  • Height in plants
  • Horned and hornless condition in cattle
  • Albinism
  • Seed shapes
  • Seed color
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13
Q

What are characteristics of albinos?

A
  • Pink eyes
  • White hair
  • Photophobia
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14
Q

What risks associated with albinism?

A

-Skin cancer
-Sun burns
-Blindness

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15
Q

What is dihybrid inheritance?

A

Inheritance of two pairs of contrasting characteristics

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16
Q

State examples of the deviations from Mendelian laws

A
  1. Linkage (linked genes)
  2. Multiple alleles
  3. Incomplete dominance
  4. Co-dominance
  5. Lethal genes
  6. Epistasis
  7. Gene complex
  8. Pleiotropy
  9. Polygenes
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17
Q

Define linked genes

A

Any two genes carried on the same chromosome

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18
Q

What is linkage?

A

Linkage is a phenomenon in which genes carried on the same chromosome, fail to separate during meiosis, and are therefore inherited together as inseparable units

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19
Q

True or false;
Chances of crossing over increase with increasing distance of the two gene loci

A

True

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20
Q

What are recombinants?

A

These are new gene combinations among offspring, different from the parental genotype.

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21
Q

Define crossover value

A

This is the percentage of offspring that show recombination

22
Q

What is epistasis?

A

This is a condition in which one gene suppresses the effect of another gene located on different loci

23
Q

What name is given to the gene that suppresses the other in epistasis?

A

Epistatic /inhibiting gene

24
Q

What name is given to the gene that is suppressed in epistasis?

A

The hypostatic gene

25
Q

What is incomplete dominance?

A

This is a phenomenon, where equal expression leads to formation of a completely new phenotype.

26
Q

Define co-dominance

A

In this case, both alleles fail to show complete dominance or recessiveness, but instead are equally expressed in the phenotype

27
Q

What antigens are found on the cell surface membrane of red blood cells of blood group, A, B, AB and O respectively?

A

Blood group A- antigen A

Blood group B- antigen B

Blood group AB- antigen AB

Blood group O- no antigens

28
Q

Which antibodies are found in each of the blood groups?

A

Blood group A- antibody b

Blood group B- antibody a

Blood group AB- no antibodies

Blood group O- antibody a and b

29
Q

What are sex linked characteristics?

A

These are characteristics that are determined by genes, carried on sex chromosomes, and only limited to a given sex

30
Q

Defined the term twins and explain the two types of twins

A

Twins are two babies born from one mother as a result of the same pregnancy

Identical twins are two babies from one egg and one sperm cell

Fraternal twins are two babies from two eggs and two sperm cells

31
Q

What are sex limited characteristics?

A

These are characteristics that are determined by genes carried on autosomal chromosomes, not affected by sex

32
Q

What is hemophilia?

A

This is a condition in which the blood of an affected person takes too long to clot, or has a reduced ability to clot due to lack of one of the clotting factors

33
Q

What are lethal genes?

A

These are genes that cause lethal effects, or death of organisms, possessing such genes

34
Q

Define mutation

A

A mutation is a change in the amount, arrangement or structure of the DNA of an organism

35
Q

Explain the two types of mutation

A
  1. Chromosomal mutation (aberration)
    - Change in the amount or arrangement of DNA
  2. Gene mutation (point mutation)
    - Change in structure of DNA at a single locus
36
Q

What are the causes of mutation?

A
  • High energy electromagnetic radiation
  • Mutagenic high energy particles
  • Chemical substances
  • Drugs
  • Food preservatives
  • Pesticides
37
Q

What are the two types of chromosomal mutations?

A
  1. Aneuploidy
  2. Polyploidy/ Euploidy
38
Q

Define aneuploidy

A

This is the loss or gain of a single chromosome

39
Q

Define euploidy/ polyploidy

A

This is the condition in which the cells of an organism possess extra sets of chromosomes beyond the normal diploid number

40
Q

What is non-disjunction?

A

This is the failure of a pair or pairs of homologous chromosomes to separate during anaphase one of meiosis

41
Q

What is aneuploidy?

A

This is a condition in which half of the gametes formed during meiosis contain extra number of chromosomes while, the other half have a chromosomes missing

42
Q

What is a polygenic trait?

A

This is a trait in which the phenotype is controlled by more than one gene.

43
Q

What is pleiotropy?

A

This is a phenomenon in which a single gene influences (affects) two or more distinct phenotypic traits.

Or; Expression of multiple traits by a single gene

44
Q

Give an example of a pleiotropic trait

A

-Sickle cell anemia
-Albinism

45
Q

Give examples of a polygenic trait

A
  • Human height
  • Human hair color
  • Human skin color
46
Q

What is genetic drift?

A

Loss of genes from a small population or the change of gene frequency of a small population by chance alone and not natural selection which results into the change of the gene frequency of the small population.

47
Q

What is gene frequency?

A

How common an allele is in a population

48
Q

What is a gene pool?

A

Total variety of genes and alleles present in a sexually reproducing population.

49
Q

What are the causes of variation in man?

A
  1. Independent assortment
  2. Crossing over
  3. Random fertilization
  4. Mutation
  5. Genetic drift
  6. Cross breeding
50
Q

What is evolution?

A

This is a gradual process by which new species are formed from pre-existing less differentiated species over a period of time due to changes in the prevailing environmental conditions.

Or;

The change, over a long time, in the genetic composition of a population which leads to the emergence of new species.

51
Q

Define natural selection

A

A process by which organisms that are better adapted to their environment survive while those that are less adapted are eliminated.

UACE Biology (20 decks)

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