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40 Cards in this Set
- Front
- Back
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What are true-breeding individuals?
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Individuals that if self-crossed, produce progeny only with parental phenotype
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What is Mendel's First Law? What does it state?
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Law of Segregation: an organism has 2 alleles for each inherited trait; one from each parent.
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What is a monohybrid cross?
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Cross in which only one trait is being studied
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What is a Fillial Generation?
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Progeny
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If the F1 generation of a PP x pp cross is self-crossed, what will be the F2 genotypic and phenotypic ratios?
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Genotype: 1:2:1 (1PP:2Pp:1pp)
Phenotype: 3:1 (3 purple:1 white) |
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For the testcross Ax x aa, what would be the genotypic and phenotypic ratios if the unknown genotype were homozygous? Heterozygous?
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AA:
Genotype: 100% Aa Phenotype: 100% Dominant Aa: Genotype: 1:1 (Aa:aa) Phenotype: 1:1 (Dom:Rec) |
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What is Mendel's 2nd Law? What does it state?
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Law of Independent Assortment: alleles of unlinked egnes will assort independently during meiosis.
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What is a dihybrid cross?
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Cross where parents differ in 2 traits
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What possible gametes can a parent of TTPP produce? ttpp?
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TP, tp
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What is the phenotypic ratio for the F1 progeny of a TTPP x ttpp cross?
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TTPP: TP
ttpp: tp TP x tp -> 100% TtPp Phenotypically dominant for both traits. |
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For a TtPp self-cross what will be the phenotypic ratios of the F1 progeny?
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9:3:3:1
(DomDom:DomRec:RecDom:RecRec) |
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For TTPP x ttpp, what is the probability that the total F2 progeny will be TTPP?
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TTPP only possible from two TP gametes.
P: TTPP x ttpp F1: 100% TtPp (possible gametes: TP, Tp, tP, tp) Need Tp x TP to get TTPP Only 1/4 of F1 has TP So need two parents with TP Thus, 1/4 x 1/4 = 1/16 probability |
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For TTPP x ttpp, what is the probability that the total F2 progeny will be TtPp?
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TtPp possible from:
TP x tp Tp x tP tp x TP tP x Tp Each cross has 1/16 probability of occuring Thus: 1/16 + 1/16 + 1/16 + 1/16 = 1/4 probability |
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What characteristics define a diploid species in Mendelian genetics?
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Have chromosome pairs (homologues) such that alleles for a given trait are segragated (one allele on one chromosome, other allele on homologue)
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At what point in meiosis does segregation and independent assortment occur?
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During first meiotic division when number of chromosomes per cell goes from 2N-->N
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How do linked genes behave during assortment?
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Linked genes located on same chromosome and are usually inherited and segregated together, which may explain over-representation of parental phenotypes in progeny.
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What is genetic recombination? What is one of its possible effects on linked genes? What is its likelihood to occur dependent on?
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Physical exchange of DNA between homologous chromosomes paired during meiosis; can unlink linked genes.
Probability of genetic recombination (AKA CROSSING OVER) dep. on distance between the 2 genes |
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What are the units of recombination frequency?
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1 map unit, which = 1% recombinant frequency
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If gene X and gene Y have a recombinant frequency of 8%, and gene X and gene Z recombine 12% of the time, what are the possible distances between genes Y & Z?
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4 or 20 map units
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Define incomplete dominance.
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When phenotype of a heterozygote is an intermediate (blend) of phenotypes of homozygotes.
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Define codominance.
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When multiple alleles exist for a given gene and more than 1 is dominant.
When 2 dominant alleles present, phenotype is result of simultaneous expression of both alleles. |
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How are blood types an example of codominance?
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IaIa or Iai give Type A
IbIb or Ibi give Type B ii gives Type O BUT IaIb gives Type AB, which is a combination (NOT blend) or characteristics of A&B |
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What is penetrance?
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Percentage of individuals in population carrying allele and actually express its associated phenotype.
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What is expressivity?
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Degree to which phenotype associated with genotype is expressed in individuals who carry the allele
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In the case of recessive inherited disorder, which genotype is required for the disorder to be expressed? Carried?
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Homozygous = expressed
Heterozygous = carrier |
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During what periods of life do recessive inherited disorders tend to be lethal?
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Early
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During what periods of life do dominant inherited disorders tend to be lethal?
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Late (Huntington's)
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On what chromosome are most sex-linked genes located?
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X; seXXX-linked is XXX-linked
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Why is it that x-linked genes are more frequently expressed in males?
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Because there is no dominant allele to mask the trait in males (only have 1 x chromosome)
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If male parents are unable to pass x-linked genes onto their sons, how is it that these genes are passed to their grandsons?
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X-linked gene is passed to ALL daughters who then become carriers (unless mother also has x-linked gene); daughters then can pass it to their sons.
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In pedigrees, how are affected individuals represented? Carriers?
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Shaded, half shaded
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What is the general strategy when analyzing a pedigree?
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Look for recessive phenotype, must be homozygous! mating b/t them and other serve as testcrosses
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When should a sex-linked gene be suspected in a pedigree?
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When only males are affected
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Define nondisjunction.
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Failure of homologous chromosomes to separate during meiosis 1 OR failure of sister chromatids to separate during meiosis 2.
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Describe the consequences of a disjunctive event in a secondary spermatocyte.
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Would resuls in 1 gamete with 2 copies of chromosome (polyploid), 2 normal haploid gametes, and 1 with no copies (aneuploid)
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Define trisomy and monosomy.
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Trisomy = zygote with 3 copies of a chromosome
Monosomy = 1 copy of chromosome |
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XXY results in?
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Klinefelter's syndrome: sterile males, small testes
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XXX results in?
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Metafemales: mentally retarded, sterile
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XYY results in?
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Normal males that are usually taller and apparently more violent
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Define three possible events following chromosomal breakage.
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Duplication: Lost fragment may join homologous chromosome.
Translocation: Joins with non-homologous chromosome Inversion: rejoins with original chromosome in reverse posn. |
