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IB Biology HL > Genetics > Flashcards

Genetics Flashcards

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1
Q

what is the difference between genes, chromosomes, a genomes?

A
  • genes made of DNA (so is genome), genes contain DNA to code for 1 protein
  • genomes is the sum of total DNA
  • DNA coils chromosome
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2
Q

what is surprising about the human genomes project?

A

it only took about 10 years, predicted more genes but found only about 23,000 in humans

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3
Q

what is a gene?

A

a heritable factor that consists of a length of DNA and influences a specific characteristic

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4
Q

where are genes found?

A

they occupy a specific position on one type of chromosome

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5
Q

what do you call various forms of genes?

A

Alleles

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6
Q

how do alleles differ, and how are new ones formed?

A

differ from each other by one or a few bases only, new alleles formed by mutation

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7
Q

what is a genome and how was it sequenced?

A

the whole genetic information of an organism, sequenced in Human Genome Project

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8
Q

What causes sickle cell anemia?

A
  • due to a base sequence mutation of the gene that codes for the alpha-globin polypeptide in hemoglobin
  • hemoglobin and red blood cells damaged, resulting sickle cells damage tissue by blocking blood flow in capillaries
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9
Q

how does the number of humans genes compare to other species

A

we have about the same number as a small plant, less than a chimp

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10
Q

whats the difference between prokaryote and eukaryote DNA?

A

Prokaryote:
- one chromosome consisting of circular DNA molecule
- some have plasmids (eukaryotes do not)

Eukaryote:
- chromosomes are linear DNA molecules associated with histone proteins
- there are different chromosomes that carry different genes

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11
Q

what are homologous chromosomes?

A

they carry the same sequence of genes but not necessarily the same alleles of these genes

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12
Q

difference between diploid and haploid nuclei? (in terms of chromosomes)

A

diploid have pairs of homologous chromosomes, haploid have one chromosome of each pair

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13
Q

what is the importance of sex chromosomes?

A
  • the number of sex chromosomes is a characteristics feature of members of a species
  • sex is determined by sex chromosomes (autosomes are chromosomes that do not determine sex)
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14
Q

what did Mendel do?

A

discovered that principles of inheritance with experiments in which large numbers of pea plants were crossed.

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15
Q

what are gametes?

A

haploids, so contain one allele of each gene

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16
Q

what happens to alleles during meiosis?

A

two alleles of each gene separate into different haploid daughter nuclei

17
Q

what does the fusion of gametes create?

A

results in diploid zygotes with two alleles of each gene that may be the same allele (homozygous) or different alleles (heterozygous)

18
Q

what do dominant alleles do?

A

mask the effects of recessive alleles, but co-dominant alleles have joint effects

19
Q

what causes genetic diseases?

A
  • many due to recessive alleles of autosomal genes
  • some are sex-linked
  • some due to dominant or co-dominant alleles
20
Q

why is the pattern of inheritance different with sex linked genes?

A

their location on sex chromosomes

21
Q

how common are genetic diseases?

A
  • most are rate
  • radiation and methanogenic chemicals increase mutation rate and can cause genetic disease and cancer
22
Q

describe inheritance in ABO blood groups

A
  • ABO blood is co-dominant, you can have A, B, AB or O
  • written in IA IA if homozygous, IAi if heterozygous, or ii if O blood type
23
Q

describe sex linked inheritance ?

A
  • typically carried on x-chromosomes, typically pass mother to son
  • girls can get sex linked-recessive disorders, but have to get allele from both parents
  • common in colorblindness and hemophilia
24
Q

describe the inheritance of cystic fibrosis and Huntington’s disease

A
  • cystic fibrosis autosomal recessive on chromosome 7
  • Huntington’s dominant, caused by mutation in one of 2 copies of HTT gene on 4th chromosome
25
Q

describe consequences of radiation after nuclear bombing and accidents

A
  • studies of Hiroshima and Nagasaki show no evidence of increased birth defects due to bombing
  • Chernobyl studies show radiation in wildlife, high rates of thyroid cancer in humans, no evidence for increase of other cancers
26
Q

how to analyze a pedigree chart?

A
  • women are circles, men are squares, non-binary are diamonds
  • dark shape shows person affected by the trait
  • people with recessive allele but don’t have trait called “carriers”
  • generations labeled with roman numerals, people numbered left to right
  • can calculate probability that couple will have child with particular trait
27
Q

what is the difference between linked and unlinked genes?

A
  • unlinked separate independently due to meiosis
  • genes are linked if they are on same chromosome
28
Q

what can gene variation be?

A
  • discrete or continuous, phenotypes of polygenic characteristics tend to show continuous variation
29
Q

what do chi-squared tests determine?

A
  • whether the difference between observed and expected frequency distribution is statistically significant
30
Q

what are dihybrid crosses and how are they analyzed in a Punnett grid?

A
  • occur between organisms that are heterozygous for 2 traits
  • set up parent vs parent
  • determine 4 possible gametes of each parent and set up Punnett grid
  • typical ratio is 9:3:3:1 for simple dominance
31
Q

describe Morgan’s discovery of non-mendelian rations in fruit flies

A
  • if genes are linked on same chromosome, they will not follow 9:3:3:1 ratio
  • using fruit flies, Morgan discovered 1:2:1 and 3:1 ratio with straight linkage, through this does not always happen due to crossing over
32
Q

what are polygenic traits?

A
  • traits influenced by environment factors, such as human height
  • a trait whose phenotype is influences by more than one gene
33
Q

how to calculate predicted genotypic and phenotypic ratios of dihybrid unlinked crosses?

A
  • multiply the probability of two events to find probability 2 independent events will both occur
34
Q

how do you identify recombinants in linked gene crosses?

A
  • recombinants are genes that are crossed over
  • offspring showing a mixture of parents, or gametes that don’t match either parents are recombinants
35
Q

how to calculate recombinant frequency?

A
  • # or recombinants / total # of genes x 100%
  • usually recombinants are the smaller values
  • the closer 2 genes are on a chromosome, less likely to recombine
36
Q

how to use chi-squared on dihybrid crosses?

A
  • multiply # or phenotypes by correct cross ratio (9:3:3:1), so 9/16 times X
  • plug these observed and expected values into formula
  • degrees of freedom = # of phenotypes -1
  • chi-squared value less than critical = independence, greater chi-squared is assumed linked genes
37
Q

what is epistasis?

A
  • when a gene at one locus alters the phenotypic expression of a gene at a second locus
38
Q

explain the genetic causes, symptoms, potential treatment, and 1 interesting fact for sickle cell disease

A
  • cause: HBB gene on chromosome II produced beta-globin protein with an altered shape, causing red blood cells to be rigid and elongated
  • follows autosomal recessive inheritance (heterozygus advantage)
  • symptoms: some resistance to malaria, pain or damage to organs, spleen, liver, kidney, lungs affected. often leads to anemia
  • treatments: antibiotics can prevent infections, folic acid supplements to produce more red blood cells
  • blood transfusion and bone marrow transplant in serious conditions
  • fact: sickle cells usually line 10-20 days whereas normal red blood cells about 120 days

IB Biology HL (13 decks)

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