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60 Cards in this Set
- Front
- Back
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what is the basic unit of heredity?
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the gene
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what are genes composed of?
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DNA
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genes are composed of DNA, which is located on what?
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chromosomes
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alternative forms of the same gene are called what?
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alleles
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the genetic makeup of an individual is called what?
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genotype
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the physical manifestation of the genetic makeup of an individual is called what?
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phenotype
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what does Mendel's law of segregation state?
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each organism has two alleles for each inherited trait. During the formation of gametes in meiosis, the two alleles separate resulting in gametes that carry only one allele for any given trait.
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what does Mendel's law of dominance state?
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in an organism that is heterozygous, the dominant allele is expressed.
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what is a monohybrid cross?
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a cross between two organisms that are each hybrid for a trait, where only one trait is being studied.
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what is the ratio of homozygous/heterozygous in every monohybrid cross?
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homo dominant 25%
hetero 50% homo recessive 25% (AKA 1:2:1) |
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what is a punnett square?
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a way to predict the genotypes (& frequencies) expected from a cross.
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what is a test cross/back cross?
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a way to determine the genotype of an individual expressing the dominant phenotype
(because it can either be heterozygous dominant, or homozygous) Aa & AA will both give phenotype 'A' whereas only aa will give phenotype 'a' |
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how is a test cross performed?
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an organism with a dominant phenotype of unknown genotype (either BB or Bb) is crossed with a phenotypically recessive organism (bb)
If any of the offspring show the recessive trait, then the parental genotype must be hybrid ( Bb) |
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when does the law of independent assortment apply? what do you call a cross performed under such conditions?
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when a cross is performed between two organisms that are hybrid for two different traits that ARE NOT ON THE SAME CHROMOSOME. -called a dihybrid cross
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what is the law of independent assortment?
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during gamete formation, the alleles of a gene for one trait, such as height, segregate independently from the alleles of a gene of another trait, such as seed color.
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if two traits on different chromosomes are linked, what happens?
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the genes will not assort independently (do not follow law of independent assortment)
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what can disrupt the correlated outcome of 2 linked genes?
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crossing over (ex: freckles & red hair are linked but you can get brunettes with freckles)
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what is a dihybrid cross?
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a cross between individuals that are hybrid for two different traits
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what is a punnett square?
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a way to predict the genotypes (& frequencies) expected from a cross.
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what is a test cross/back cross?
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a way to determine the genotype of an individual expressing the dominant phenotype
(because it can either be heterozygous dominant, or homozygous) Aa & AA will both give phenotype 'A' whereas only aa will give phenotype 'a' |
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how is a test cross performed?
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an organism with a dominant phenotype of unknown genotype (either BB or Bb) is crossed with a phenotypically recessive organism (bb)
If any of the offspring show the recessive trait, then the parental genotype must be hybrid ( Bb) |
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when does the law of independent assortment apply? what do you call a cross performed under such conditions?
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when a cross is performed between two organisms that are hybrid for two different traits that ARE NOT ON THE SAME CHROMOSOME. -called a dihybrid cross
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what is the law of independent assortment?
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during gamete formation, the alleles of a gene for one trait, such as height, segregate independently from the alleles of a gene of another trait, such as seed color.
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if two traits on different chromosomes are linked, what happens?
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the genes will not assort independently (do not follow law of independent assortment)
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what can disrupt the correlated outcome of 2 linked genes?
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crossing over (ex: freckles & red hair are linked but you can get brunettes with freckles)
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what is a dihybrid cross?
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a cross between individuals that are hybrid for two different traits
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what is the phenotypic ratio of a dihybrid cross? (AABB x aabb)
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9:3:3:1
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what is incomplete dominance characterized by?
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blending of parental phenotypes
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what's an example of incomplete dominance?
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a white flower (WW) crossed with a red flower (RR) produces a pink flower (RW)
where neither trait is dominant. |
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what's the difference between incomplete dominance and codominance?
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incomplete dominance is a blending. (neither are dominant!)
codominance results in the expression of both traits (both are dominant!) |
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what is codominance?
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when multiple alleles exist for a given gene, and more than one of them is dominant.
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what is the classic example of codominance & multiple alleles?
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the inheritance of ABO blood groups in humans. (A, B, AB, O) exemplifies multiple alleles, and the codominance of AB blood type exemplifies codominance.
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how many chromosomes do humans have? how many are autosomes? sex chromosomes?
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46 total (23 pairs)
44 (22 pairs) autosomes 2 sex chromosomes |
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do men or women have homologous XX?
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women
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do men or women have heterologous XY?
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men
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what determines the gender of the zygote?
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the male contribution- because women only and always contribute an X
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genes on the X or Y chromosome are called what?
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sex-linked
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most sex-linked genes are located on what?
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the X chromosome
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who do x-linked recessive diseases effect? why?
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males- because unless a daughter gets an affected X chromosome from mom AND dad, she will only be a carrier.. whereas men only have one X, thereby expressing the diseased phenotype
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what is nondisjunction?
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the failure of of homologous chromosomes to separate during meiosis I or the failure of sister chromatids to separate during meiosis II.
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Majority ("subjective") rule of entrapment
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It occurs only if:
1) D. was not predisposed to commit crimes of the sort charged; and 2) Officers created the intent to commit the offense in her mind Minority ("objective") rule of entrapment: Policy activity would cause a reasonable and unpredisposed person to form the intent to commit the crime. *Just look at what officer does |
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what is Down syndrome?
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trisomy of the chromosome 21
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what is pleiotropy?
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one gene has more than one affect.
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what is an example of pleiotropy?
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the allele for the coloration of siamese cats is the SAME allele that causes many siamese cats to be cross-eyed.
(note: they are NOT LINKED... they are the SAME gene!) |
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what is epistasis?
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two separate genes control one trait, BUT ONE GENE MASKS THE EXPRESSION OF THE OTHER.
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in epistasis, which gene is said to be epistatic?
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the gene that masks the other gene is epistatic.
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what is polygenic inheritance?
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traits such as hair color, height and skin color result from blending of several genes that vary along a continuum.
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what are linked genes?
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genes on the same chromosome!
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how many linkage groups do humans have?
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46
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what is a chiasma?
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the site at which a crossover event occurs
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what is recombination?
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the result of crossover
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what is X-inactivation?
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the deactivation of one of a females X chromosomes early in development in every somatic cell.
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what is a barr-body?
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the inactivated X chromosome in every somatic cell in the female body.
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are all somatic cells of the female body identical?
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no.. because the same X chromosome isn't inactivated in every cell.
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what's an example of proof of x-inactivation?
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calico cats- female, have patches of yellow and black fur. because of random inactivation of Xchromosomes
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what two general types of mutations are there?
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1. gene mutations
2. chromosomal mutations. |
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what are the characteristics of gene mutation?
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-change in DNA sequence
-can not be seen under microscope. |
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what are some examples of chromosome mutation?
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-can be seen under microscope (karyotype)
-down syndrome -turner's syndrome -klinefelter's syndrome. |
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what is extranuclear inheritance?
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the inheritatnce of genes from mitochondira (always from mother) which have adverse effects on ATP production
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do sister chromatids cross over?
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NO ...they are genetically identical
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