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Biology SL > 3.4 Inheritance > Flashcards

3.4 Inheritance Flashcards

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1
Q

What was Gregor Mendel experiment with pea plants? (3)

A
  • first, crossed different varieties of purebred pea plants, then collected and grew the seeds to determine their characteristics
  • next, he crossed the offspring with each other (self-fertilisation) and grow their seeds to similarity determine their characteristics
  • these crosses were performed many times to establish reliable data trends (5000 crosses were performed)
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2
Q

What did Mendel discover from these experiments? (2)

A
  • when he crossed 2 different purebred varieties together the results were not a blend (only one features would be expressed)
    (Purebred tall and short pea plants crossed, all offspring developed into tall growing plants)
  • when Mendel self-fertilised the offspring, the resulting progeny expressed the 2 different traits in a ration of -3:1
    (When tall growing progeny were crosses, tall and short pea plants were produced in a ration - 3:1)
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3
Q

What conclusions did Mendel draw from the results of his experiment? (5)

A
  • organisms have discrete factors which determine features (genes)
  • organisms possess 2 versions of each factor (alleles)
  • each gamete contains 1 version of each factor (sex cells are haploid)
  • parent contribute equally to the inheritance of offspring as a result of fission between randomly selected egg and sperm
  • for each factor, one version is dominant over another and will be completely expressed if present
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4
Q

What are Mendels laws? (3)

A
  • law segregation: when gametes form, alleles are separated os each gamete carries only 1 alleles for each gene
  • Law of independent assortment: the segregation of alleles for one gene occur independent to that of any other gene
  • Principle of dominance: recessive alleles will be masked by dominant alleles
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5
Q

What are caveats to Mendels? (2)

A
  • law of independent assortment does not hold true for genes located on same chromosome
  • not all genes show a complete dominance hierarchy - some genes show co-dominance or incomplete dominance
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6
Q

What are gametes?

A

Haploid sex cells formed by process of meiosis

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7
Q

Describe why haploid sex cells are haploid (3)

A
  • during MI, homologous chromosomes are separated into different nuclei prior to cell division
  • as homologous chromosomes carry the same gene, segregation of the chromosome also separate allele pairs
  • as ganteries contain only 1 copy of each chromosome they carry only 1 allele for each gene
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8
Q

What does it mean if gametes are haploid?

A

The only possess 1 allele for each gene
- male and female gametes fuse during fertilisation the zygote will contain 2 alleles for each gene

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9
Q

How many alleles for each gene are located on a sex chromosome?

A

Males have only 1 allele for each gene on the sex chromosome as the chromosomes aren’t paired

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10
Q

How can combinations of alleles be categorised? (3)

A
  • if the maternal and paternal alleles are the same, the offspring is homozygous for the gene
  • if the maternal and paternal alleles are different, the offspring is heterozygous for the gene
  • males only have 2 allele for each gene located on a sex chromosome and are hemizygous for that gene
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11
Q

What the gene composition for a specific trait called?

A

Genotype
(Either heterozygous or homozygous)

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12
Q

What is there observable characteristics of a specific trait called?

A

Phenotype

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13
Q

What is the phenotype determined by?

A
  • genotype and environmental influences
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14
Q

What will the dominant allele do? (3)

A
  • dominant allele will mask the recessive allele when in a heterozygous state
  • homozygous dominant and heterozygous forms will be phenotypically indistinguishable
  • the recessive allele will only be expressed in the phenotype when in a homozygous state
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15
Q

What is co-dominance?

A

Occurs when pairs of alleles are both expressed equally in the phenotype of a heterozygous individual

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16
Q

What kind of allele dominance do blood type A and B have?

A

Co-dominant

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17
Q

How do genetic diseases occur?

A

When mutations to a gene abrogate normal cellular function leading to the development of a disease phenotype

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18
Q

Only what kinds of alleles will result in an autosomal genetic diseases to occur?

A

Homozygous (both alleles are faulty)

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19
Q

What will occur to a heterozygous person with an recessive disease carrying allele?

A

They will not develop the disease
They will be carriers

20
Q

What is an example of an autosomal recessive disease?

A

Cystic fibrosis

21
Q

What is the type of allel which only requires one allele to cause a genetic disease?

A

Dominant alleles

22
Q

What is an example of an autosomal dominant genetic disease?

A

Huntington’s disease

23
Q

What occurs is a genetic disease is co-dominant alleles?

A

Only requires one copy of the faulty for the disease to occur

24
Q

What kind of disease result will heterozygous individuals with co-dominant allele diseases have?

A

Milder symptoms due to the moderating influence of a normal allele

25
Q

What is an example of a co-dominant genetic disease?

A

Sickle cell anemia

26
Q

What is cystic fibrosis? (3)

A
  • autosomal recessive disease caused by mutation of the CFTR gene on chromosome 7
  • produce more mucus which is unusually thick and sticky
  • heterozygous carriers will not develop disease symptoms
27
Q

What are the symptoms of cyctic fibrosis?

A

Muscus clogs airways and secretory ducts of the digestive system leading to respiratoyy failure and pancreatic cysts

28
Q

What is Huntington’s disease? (3)

A
  • autosomal dominant disorder caused to (HTT) Huntington gene on chromosome 4
  • HTT possess a repeating tri nucleotide sequence (CAG), over 28 repeats is unstable and causes sequence to amplify
  • usually occurs in late adulthood
29
Q

Why may recessive be more common?

A

Faulty alleles can be present in carriers without causing disease

30
Q

What does sex-linkage mean?

A

Gene controlling characteristic found on a sex chromosome

31
Q

Why do Y chromosomes have only a few genes compared to X?

A

Shorter than X

32
Q

Why are sex-linked genes more likely to be X-linked?

A

X is much longer with more genes (which may not be found on Y)

33
Q

Why are sex-linked inheritance patterns different from autosomal patterns?

A

Chromosomes aren’t paired in males (XY)

34
Q

Why are sex-linked dominant traits more common in females?

A

Females have 2 X chromosomes which can be homozygous or heterozygous

35
Q

What are kind of X-linked traits do males have and why? (2)

A

Hemi yogis X-linked trait
- have only one X chromosome

36
Q

Why are X-linked recessive traits more common in males?

A

The condition cannot be linked by a second allel

37
Q

Why at are the trends for X linked conditions? (3)

A
  • openly females can be carries, males cannot be heterozygous carriers
  • males will always inherit an X-linked trait from their mother (get Y from father)
  • females cannot inherit an X-linked recessive contusion from an unaffected father (receive dominant allele)
38
Q

What are examples of X-linked recessive conditions?

A

Red-green colour blindness
Haemophilia

39
Q

What is haemophilia? (3)

A
  • genetic disorder where the body’s ability to control blood clotting
  • blood clotting is controlled by coagulation factors on the X chromosome
  • one of the factors becomes defective
40
Q

what is red-green colour blindness? (2)

A
  • Genetic order where people can’t tell between green and red hues
  • caused by mutation to the red-green retinal photoreceptors on X chromosome
    (Diagnosed using Ishihara test)
41
Q

what is a gene mutation?

A

change to the base sequence of the gene that can affect the structure and function of the protein it encodes

42
Q

what are 3 examples of factors which can induce mutations?

A
  • Radiation - eg.UV radiation from sun, gamma
  • Chemical - eg. reactive oxygen species, alylating agents (cigarettes)
  • Biological Agents - eg. bacteria
43
Q

what is the name of agents that increase the rate of genetic mutations called?

A
  • mutagens
44
Q

what are 2 examples which led to the catastrophic release of radioactive material?

A

Hiroshima nuclear bomb
Chernobyl accident

45
Q

what are long term consequences of radiation? (3)

A
  • increased incidence in cancer development
  • reduced T cell counts and altered immune functions leading to higher rates of infection
  • organ-specific health effects
46
Q

what are the consequences of radiation exposure at Chernobyl and Hiroshima?

A

Chernobyl- thyroid disease was a common consequence of the accident due to the release of radioactive iodine
- there was no significant increase in birth defects following the Hiroshima bombing

Biology SL (38 decks)

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