d3.2 (inheritance) Flashcards
define zygote
the diploid cell produced at fertilization when gametes fuse
where are male gametes found in flowers?
in pollen grains on the flower anther
where are female gametes found in flowers?
inside the ovules of the flower ovary
watch a video on mendel’s pea plants
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define phenotype plasticity
an organism’s ability to change its phenotype in response to environmental conditions
example of phenotype plasticity: butterworts (plant)
how does their morphology differ in nutrient rich vs poor conditions?
rich : large leaves for photosynthesis
poor : smaller leaves for capturing & digesting insects
ways phenotype plasticity manifests itself in animals (3 ways with example of garter snakes)
coloration = to absorb/reflect light to maintain body temperature
metabolic rate = varies with temp, affecting activity level, feeding freq & energy use
reproductive timing = warmer temps may accelerate development & increase freq of reproductive cycled
define autosomal (for genetic diseases) & effect pattern
the gene is located on an autosome, so males and females are equally affected
define sex-linked (for genetic diseases) & effect pattern
the gene is located on a sex chromosome, resulting in a different pattern of inheritance in males and females
2 main examples of sex-linked genetic diseases
red-green colour blindness
haemophilia
what does disease phenylketonuria (PKU) cause?
phenylalanine from the diet is not processed effectively as an allele that codes for a non-functioning phenylalanine hydroxylase is present (may cause brain damage if excessive amounts of phenylalanine are taken in)
what is the treatment for PKU?
a diet containing little or no phenylalanine (an amino acid in plant and animal foods, such as meat, eggs, fish, and soy products)
what is a SNP?
single nucleotide polymorphism (a variation at a single position in a DNA sequence)
if a SNP occurs within a gene, then the gene is described as having what?
more than 1 allele
an example of a gene with multiple alleles in the gene pool is called the “s-gene”. where is it found & how many known alleles are there?
the gene pool of many tree fruit crops
over 50 known alleles
define cultivar
a variety of a plant for which people have selected for desired traits and which retains those traits when propagated
in species with the s-gene, what process is necessary to achieve sexual reproduction? explain how this works
cross-polination
during pollination, if a pollen lands on the stigma of a flower with the same allele of the s-gene, the pollen is rejected and fertilization will not occur.
what are the 3 ABO blood type alleles?
Iᴬ , Iᴮ , i
how do the 3 different blood type alleles each alter the glycoprotein on the red blood cell membrane?
Iᴬ = adds molecule acetylgalactosamine
Iᴮ = adds molucule galactose
i = does not add anything
sometimes one allele is not completely dominant over the other alleles of a gene– what is this called? what type of phenotype is caused?
incomplete dominance
an intermediate heterozygous phenotype
example of incomplete dominance (petals)
in snapdragons, colour is influenced by a gene with 2 alleles, red (Cᴿ) and white (Cᵂ). upon cross pollination between two homozygous parents with each of these two alleles, offspring will have pink flowers (CᴿCᵂ)
example of codominance (coat colour)
roan coat color in many organisms is the result of having red hair (Cᴿ) interspersed with white hairs (Cᵂ)
what typically triggers male development? why? what formation is initiated?
presence of a Y chromosome, due to SRY gene, initiates testes formation
deducing patterns of inheritance from pedigree charts
the trait skips generations = ?
the trait found much more in males = ?
recessive, sex-linked
features of discrete variation within a species x3 & examples
phenotypes that can be put into distinct qualitative categories with no intermediates between them
influenced by only one or a few genes
not significantly influenced by the environment
i.e. blood type, medel pea plant stem height
features of continuous variation within a species x3 & examples
phenotypes that vary along a quantitative continuum with a range of phenotypes possible
results from complex interaction between many different genes (“polygenic”)
the environment influences the expression of the phenotype
i.e. human height & skin colour
why do mendel’s pea plants have stem height as an example of discrete variation? what controls it to make it discrete?
pea plants were either tall or dwarf, with no intermediate heights
the pea plant stem height gene, Le, codes for a protein that is required for the production of a plant growth hormone called gibberellin
how and where is melanin produced? how many genes are involved in human skin colouration?
made within small membrane–bound packages called melanosomes within skin cells. 169 genes are involved
how does environment affect skin colour?
exposure to sunlight stimulates melanocytes to produce additional melanin.
melanin absorbs UV radiation so that it does not penetrate deep into the skin
what impact can too much UV exposure do (adaptation of more melanin in skin)?
what impact can too little UV exposure do (adaptation of less melanin in skin)?
too much = folate deficiency → neurological abnormalities in fetal development
too little = vitamin D deficiency → reduced Ca2+ absorption and brittle bones
read over d3.2.16 save my exams notes
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define linked vs unlinked genes
linked: genes located close to each other on the same chromosomes (genes move together through meiosis)
unlinked: independently assorted; genes on different chromosomes
define dihybrid cross
a genetic cross between two individuals with two observed traits that are controlled by two unlinked genes
in mendel’s pea plants, how many possible unique gametes created from a RrYy plant (round yellow)?
4: RY, Ry, rY, ry
do a few practice dihybrid cross punnet grids
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what is linked gene notation?
look up image
watch a video on linked genes
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do a few practice linked genes punnet grids
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define recombinant
an offspring with a different combination of alleles than those found in either parent
what are recombinants the result of?
the processes of meiosis that lead to genetic variation (i.e. independent assortment of unlinked genes during metaphase 1 and/or crossing over between linked genes during prophase I)
new combinations of alleles of genes on the same chromosome can be produced during what phase?
prophase I of meiosis
how does distance between linked genes change the probability of recombinant offspring?
the greater the distance between two genes, the more likely a crossover will occur between them
do a few practice of crossing over of linked genes punnet grids
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