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Cell Biology & Genetics > VARATION > Flashcards

VARATION Flashcards

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1
Q

Define Varation

A

Variation is the differences between individuals within a species

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2
Q

State the causes of variation

A

Causes of variation

  • Crossing over
  • Independent Assortment
  • Mutation
  • Fertilization
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3
Q

What is crossing over and when do it occur

A

When two chromosomes exchange genetic material

  •  Occurs during prophase I of meiosis, homologous chromosomes swap genes.
  • As a result, each offspring will have a new combination of traits different from the parent and any other offspring.
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4
Q

What is Independent Assortment

A

The random alignment of homologous chromosomes during metaphase I

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5
Q

Define Mutation

A

Mutations are changes in the genetic make up of an organisms.

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6
Q

Define Mutagen and give examples

A

Any substance or chemical that causes a mutation.
Examples of mutagens include radioactive substances, x-rays, ultraviolet radiation, and certain chemicals

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7
Q

Define Gene Mutation

A
  • A gene mutation involves a change in the order of the bases (A, C, G, 1) that make up the gene
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8
Q

what are the four bases in DNA

A

The four bases in DNA are adenine (A), cytosine (C), guanine (G), and thymine (T).

(A with T, and G with C) (URACIL IN RNA SUB T )

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9
Q

What are the three types of gene mutation

A

There are three types of gene mutations:

  • Deletion (base missing)
    AGTCTGC -> AGCTGC
  • Addition (extra base added)
    AGTCTGC -> AGTCGTGC
  • Substitution (one base is substituted for another)
    AGTCTGC -> AGGCTGC
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10
Q

What are the disorders caused by gene mutation?

A
  • Cystic fibrosis
  • Sickle cell anemia
  • Hemophilia
  • Huntington’s Disease
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11
Q

What is Chromosome Mutation?

( GIVE EXAMPLES)

A
  • A chromosome mutation is a change in the structure or arrangement of a chromosome.
  • Examples include: Down’s Syndrome, Cri du chat syndrome, Turner’s syndrome, klienfelter syndrome
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12
Q

What is Fertilization?

A

fertilization is the fusion of the nuclei of both sperm and egg cells to form a zygote

  • Since fertilization is a random process, there are many possible different combinations of genes in a zygote.
  • E.g. the sperm that fertilizes an egg determines whether the new offspring will be a boy (XY) or girl (XX)
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13
Q

What are the types of variation?

A
  • Continuous Variation
  • Discontinuous Variation
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14
Q

What is Continuous variation

A
  • In continuous variation there is a complete range of measurements from one extreme to the other.
  • Height is an example of continuous variation - individuals can have a complete range of heights, for example, 1.6, 1.61, 1.62, 1.625 etc meters high.
  • Continuous variation in a group of individuals can be shown using a histogram or line graph.
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15
Q

Provide examples of continuous variation

A
  • Weight
  • Hand span
  • Shoe size
  • Milk yield in cows
  • Hair, eye, and skin color
  • Arm length
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16
Q

What is Discontinuous Variation

A
  • is when individuals fall into a number of distinct classes or categories, and is based on features that cannot be measured across a complete range. You either have the characteristic or you don’t.
    • A bar graph is used to represent discontinuous variation.
17
Q

Provide Examples of discontinuous variation include:

A
  • Blood group
  • Gender
  • Tongue rolling
  • Attached ear lobes
  • Widows peak
18
Q

Define Natural Selection

A
  • the process whereby organisms better adapted to their environment tend to survive and produce more offspring. This is dominated by environmental factors.
19
Q

What is the Evolution by Natural Selection

A
  • Struggle for existence
  • Members of each species compete for food, space, and necessities of life.
  • Predators that can run faster to catch more prey
  • Prey that are better camouflaged avoid being caught.
20
Q

EXAMPLES OF NATURAL SELECTION (sickle cell anemia)

A
  • Sickle Cell Anemia

Sickle Cell Anemia is a mutation that has provided an advantage in Malaria prone areas.

In these areas it is favored by natural selection and therefore Sickle Cell Anemia persists in many heterozygous individuals since the homozygous recessive condition is lethal.

21
Q

What is Natural Selection- Phenotypic ratio

A
  • Changes in the physical environment and predation reduce the number of organisms with certain features (those not adapted)
22
Q

What is Artificial Selection?

A
  • *Artificial selection (selective breeding) - This is when humans choose parents with particular characteristics to breed together and produce offspring with more desirable characteristics. Selecting breeding may include ranchers breeding cows and buffalo to get a certain kind of meat.
  • It may also include mating male and female English Bull dogs that exhibit characteristics and selling their off spring.
23
Q

Explain Artificial Selection- Phenotypic ratio

A
  • Humans select for and against features in pets and plants… changing the phenotypic ratio
  • Artificial Selection is also known as Selective breeding.
24
Q

Differentiate between Natural Selection vs. Artificial Selection

A
  • Natural Selection
  • Dominated by environmental factors
  • Where nature chooses organism with best traits for survival
  • Ex: tigers developed stripes to sneak up on prey
  • Artificial Selection
  • Controlled by humans, “goal-directed”
  • Person chooses which traits of the organism they want it to have
  • Ex: dogs
25
Q

Exaplain how DDT creates Resistant Insects

A

DDT was used to kill mosquitoes (stopping malaria spread)
Most insects were killed while others mutated making them resistant.
These resistant insects reproduced
Pesticide spray was less effective

Spraying with DDT produces the selective pressure which favours the resistant mosquitoes.

Because they can resist the effects of DDT, the resistant mosquitoes are said to have a selective advantage

Cell Biology & Genetics (7 decks)

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