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LS12 - Life Sciences > Genetics > Flashcards

Genetics Flashcards

0
Q

Genes

A

DNA units in chromosomes coding for a particular protein or characteristic

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1
Q

Trait

A
  • In genetics, a characteristic of an organism.
  • Some are visible e.g. Eye colour
  • Some not easily seen e.g. Blood type
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2
Q

Allele

A
  • A form of a particular gene
  • Alleles occupy the same locus of a particular chromosome
  • One gene/allele is inherited from each parent
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3
Q

Artificially crossed

A

Breeding controlled by humans, usually to create organisms with specific traits.

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4
Q

Dominant allele

A

An allele which is expressed over a recessive allele

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5
Q

Recessive allele

A

An allele not expressed in the presence of a dominant allele

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6
Q

Genotype

A

The genetic makeup of a particular organism

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7
Q

Phenotype

A
  • The observable traits,
  • determined by both genotype and the organisms environment
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8
Q

Locus

A

Specific place or position (on a chromosome)

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9
Q

Offspring

A

Children or young of particular parent(s)

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10
Q

Selective breeding

A

Intentional mating of two organisms to promote specific trait(s)

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11
Q

Self pollinate

A

Transfer of pollen from anther to stigma of same flower or plant

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12
Q

Pure/true-breeding

A

Self fertilized or two pure-breeding organisms consistently produce offspring with the same particular trait

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14
Q

Who was Gregor Mendel

A
  • Austrian monk in mid 1800’s
  • Quantitatively showed that parent plants pass on factors of inheritance (genes)
  • some factors not expressed but still able to be passed on
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15
Q

Mendel’s focus group and what he did with them

A
  • Pea plants
    • Thousands of selective breeding events e.g. forcing self and cross-pollination examining particular traits
    • Starting with true-breeding plants for a particular trait he crossed them with other true-breeding plants
    • Recorded traits of offspring
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16
Q

Why pea plants for Mendel’s experiments?

A
  • grow and reproduce quickly
  • many traits in one species
  • easy to control reproduction (naturally self-fertilizing but can be cross-fertilsed)
  • True-breeding strains for particular traits already available to him
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17
Q

Seven traits Mendel studied in peas

A
  • Seed shape
  • seed colour
  • flower colour
  • pod shape
  • pod colour
  • flower position
  • plant length
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18
Q

Mendel’s three laws

A
  • Segregation
  • Dominance
  • Independent assortment
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19
Q

Law of segregation

A
  • If there are two alleles controlling a trait, these alleles separate and go to different gametes when parent reproduces.
  • During meiosis alleles randomly divided between different gametes
  • Thus 2x2 possible combinations of the same alleles in successive generations are possible
20
Q

Law of dominance

A

If an organism has different alleles, the trait of one of these will be visible (domnant) whole the other will be hidden (recessive)

21
Q

Symbols for dominant/recessive alleles

A
  • Capital letter for dominant and lower case letter for recessive.
  • Letters with a different form of capital vs lower case are typically used
  • e.g. Dd or Tt (instead of e.g. Pp or Oo)
22
Q

Homozygous individual

A

An individual with only one kind of allele for a particular gene

23
Q

Heterozygous individual

A

An individual with two kinds of allele for a particular gene

26
Q

Law of independent assortment

A

Different traits are passed on independently of one another so that combinations of traits in parents do not always match combinations of traits in offspring.

27
Q

Two cats both have brown fur. They have the following alleles: Bb and BB. Which is the same - their genotype or phenotype?

A

Phenotype

28
Q

Two cats both have brown fur. They have the following alleles: Bb and BB. Which one is homozygous?

A
  • BB as it has the same alleles.
  • Bb is heterozygous.
29
Q

Monohybrid cross

A
  • Genetic cross between two individuals
  • Each of whom has different alleles for a single trait
  • And only two different possible alleles
  • can be heterozygous or homozygous individuals
30
Q

F1 generation

A
  • First filial
  • Filial means the relation of a child to parent
31
Q

Incomplete dominance

A
  • When alleles show incomplete or partial dominance
  • Neither characteristic is dominant over the other
  • Offspring can show a new, mixed characteristic when heterozygous
  • E.g. White flower crossed with a red flower -> pink flower
32
Q

Co-dominance

A
  • Co-existing characteristics because of equally dominant alleles
  • Both are present in the phenotype when heterozygous
  • E.g. Black cow crosses with a white cow -> spotted black and white cow
33
Q

Blood groups - type of dominance

A

Co-dominance

34
Q

Possible blood types in humans

A
  • A
  • B
  • AB
  • O
35
Q

Rhesus blood factor

A
  • Rhesus blood antigen
  • Two alleles Rh+ and Rh-
  • Rh+ is dominant and expresses a cell surface antigen
  • Rh- is recessive and does not express an antigen
36
Q

Polygenic inheritance

A
  • Traits that are determined by more than one gene
  • Results in continuous variation in a population
  • E.g. Hair colour, eye colour, intelligence
37
Q

Dihybrid crosses

A
  • Examining inheritance of two different traits at the same time
  • E.g. Flower colour AND seed shape
38
Q

Pattern of inheritance with two true breeding dihybrid individuals

A

9:3:3:1

39
Q

Pedigree diagram

A
  • Diagrams showing family relationships
  • Older generations are at the top
  • Symbols of a square = males and circles = females
  • Horizontal lines directly connecting individuals show breeding
  • Vertical lines with horizontal connectors show offspring
  • A key (shading) indicates the known phenotypes
40
Q

Pedigree diagram uses

A
  • To determine the type of inheritance
  • Evaluate the inheritance of genetic conditions in a particular family
  • By genetic councilors to advise families with genetic diseases
41
Q

Sex chromosomes

A
  • The sex of an individual is determined by the presence of X and Y chromosomes.
  • Also called gonosomes.
  • XX = female XY = male
42
Q

Chance of male vs female offspring

A
  • Determined by the sperm
  • 50% that it contains a Y-chromosome = XY male individual
  • 50% that it contains an X-chromosome = XX female individual
43
Q

Autosomes

A

Chromosome pairs 1-22 not involved in determining the sex of an individual

44
Q

Sex-linked genes

A
  • Genes carried on the sex chromosomes
  • X-chromosome has over 1000 genes
  • Y-chromosome only 78 genes
45
Q

Male risk of sex-linked disorders

A
  • Since male have only one X-chromosome they have a higher risk of a genetic disorder found on the X-chromosome.
  • Even if that disorder is recessive for females, since males have only one X-chromosome, they are still affected.
46
Q

Examples of sex-linked disorders

A
  • Muscular dystrophy
  • Haemophilia
  • Cleft palate syndrome
  • Colour blindness
47
Q

Haemophilia

A
  • X-chromosome linked
  • Recessive for females Lack of a gene for blood clotting
  • Affected individual (male with this faulty gene) bleeds excessively
  • Females homozygous for this faulty gene usually aborted before birth.
48
Q

Muscular dystrophy

A
  • A degenerative disease most common in boys.
  • X-chromosome linked recessive inheritance pattern.
  • Progressive loss of muscle function.
49
Q

Genetic counselling

A

Advised if:

  • Have a child or family history of a genetic condition, chromosome abnormality of birth defect
  • You or family have a history of miscarriages or stillbirths They help you understand risks of passing inherited conditions on to your children

LS12 - Life Sciences (33 decks)

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