UNIT 3 - D 3.2 - Inheritance Flashcards
What is the term diploid used to describe?
a nucleus that has chromosomes organized into pairs of homologous chromosomes
What are examples of exceptions to the adult form of an animal having almost all diploid cells?
male bee, wasp and ant cells are haploid
What does the variable n represent and what does it refer to?
it represents the haploid number and it refers to the number of sets of chromosomes that a nucleus can have
What did Mendel use artificial pollination to do during his famous experiments?
to get the sperm cells in the pollen of pea plants into the ovum cells inside the ovaries of other pea plants
When Mendel crossbred tall plants and short plants, which was the dominant allele?
the tall allele
What is a heterozygote?
an organism that has one dominant allele and one recessive allele for a particular trait
What can be used to show the dominant and recessive alleles for different traits?
a punnett grid
What is a punnett grid used to show?
how the alleles of parents are split between their gametes and how new combinations of alleles can show up in their offspring
What is the purpose of a punnett grid?
to show all the possible combinations of genetic information for a particular trait in a monohybrid cross
What is a monohybrid cross?
the parents have different alleles and it shows the results for only one trait
What are the steps in creating a punnett grid?
- choose a letter to represent the alleles - capital=dominant, lowercase=recessive
- Determine the parents’ genotypes - either TT, Tt, or tt
- determine the gametes that the parents could produce - TT can only make gametes with T…
- Draw a punnett grid - parents’ gametes are at the top and side of the grid
- Work out the chances of each genotype and phenotype occurring
What does TT mean for an individual’s genotype?
the genotype is homozygous dominant
What does Tt mean for an individual’s genotype?
The genotype is heterozygous
What does tt mean for an individual’s genotype?
the genotype is homozygous recessive
What is the first generation called?
`the first filial generation or F1 generation
What is the generation produced by crossing two members of the F1 generation called?
the second filial generation or the F2 generation
How many dominant alleles does a genotype need to have to produce the dominant trait?
only one dominant allele, to produce the recessive allele, there can be no dominant alleles
Why is it possible for some plants (such as peas) to self-pollinate?
they have flowers that can produce both male pollen and female ova so this is possible when they prepare gametes at the same time
What is self-pollination?
when a plant’s pllen lands on flower it has produced itself
What is possible as a result of self-pollination?
self-fertilization
What does self-fertilization result in?
less genetic diversity than cross-pollination
What can farmers use when they want plants with the same characteristics as previous generations?
self-pollination techniques
What can farmers use when they want to create new varieties of plants with combinations not seen before
cross-pollination techniques
What is an example of a common plant that has been cross bred over many years to acheive the desired combination of traits?
modern wheat
What is an allele?
one specific form of a gene
What do different alleles differ by?
one or a few bases
What is the genotype the symbolic representation of?
the pair of alleles possessed by an organism, typically represented by two letters
How will all eukaryotes that produce sexually inherit alleles?
one from the father and one from the mother
What does homozygous refer to?
having two identical alleles of a gene
What does heterozygous refer to?
having two different alleles of a gene
What is being heterozygous a result of?
when the paternal and maternal alleles are different
What is a carrier?
an individual who has a recessive allele of a gene that does not have an effect on the phenotype
What are examples of traits produced by genetics only?
ABO blood type, genetic conditions
What are examples of traits produced by the environment only?
learned behavior, acquired physical traits
What are examples of traits produced by both genetics and the environment combined?
Human height (max height is genetic, but poor nourishment may lead to shorter height), cancer (may have genetic component, could be triggered by mutagens)
What is a dominant allele?
an allele that has the same effect on the phenotype whether it is paired with the same allele or a different one
How often are dominant alleles expressed in the phenotype?
always
Why would the a in the genotype Aa not be expressed in the phenotype?
the a allele is masked, not transcribed or translated during protein synthesis
What is a recessive allele?
an allele that has an effect on the phenotype only when no dominant allele is present to mask it
What are codominant alleles?
pairs of alleles that affect the phenotype when present in a heterozygote
What is phenotype plasticity?
an organism’s ability to express its phenotype differently depending on the environment
What is an effective way of adapting?
phenotypic plasticity
What are cyclical event such as seasonal food availiblity described as?
phenological
Where does phenotypic plasticity generate changes?
physiology, morphology, behavior, phenology
How does the freshwater snail Physa virgita stay safe from its predator, the bluegill fish, Lepomis macrochirus)?
It expresses its genes slightly differently in order to grow a more rounded, shorter shell which is more difficult for the predator to crush
What is necessary for two healthy parents to have a child who is affected by a genetic condition?
both parents must be carriers of the version of the gene that causes the disease
What is phenylketonuria/PKU?
a genetic disease that is caused by mutations in the autosomal PAH gene resulting in low levels of the enzyme phenylalanine hydroxylase
What is a child at risk of if they have PKU?
if there is a large quantity of protein in their diet, the phenylalanine levels can become toxic and impair brain development
What are autosomal recessive diseases caused by?
recessive alleles
Where are the locus of autosomal recessive diseases’ gene found?
on one of the first 22 pairs of chromosomes but not on the sex chromosomes X or Y
When do SNPs occur?
when a nucleotide of the genetic code is not found where it is expected and another is found at that position instead
What may SNPs lead to?
another amino acid to be coded for which could modify the structure and properties of the protein that is translated
Why can some people taste the bitterness of PTC but others can’t?
if a person has one version of a certain gene, they can taste PTC while people with a different version cannot taste it
What are the possible blood types in humans?
A, B, AB, O
How many alleles of a gene are there to produce the four possible blood types?
3
How many genotypes can the three alleles for determining blood types produce?
6
What does I^A represent?
the alleles for producing type A antigens, resulting in type A blood
What does I^B represent?
the allele for producing type B antigens, resulting in type B blood
What does i represent?
the recessive allele that produces neither A nor B antigens, resulting type O blood
What is an example of codominance with alleles?
I^A with I^B giving type AB blood
What does incomplete dominance result in?
neither phenotype, rather something in between
For the four o’clock flower, how would its colour end up pink?
If the genotype was C^R C^W (both red and white)
Why is incomplete dominance called what it is?
because the two parent alleles are mixed and each one contributes to the phenotype but neither is masked
How does the X chromosome compare to the Y chromosome in the 23rd pair of chromosomes?
The X chromosome is longer and contains more genes
What do the genetics of being male or female depend on?
whether you inherit an X or a Y chromosome from your father
How is higher oestradiol and progesterone prodcution allowed?
by alleles that interact on both of the X chromosomes of female embryos
What are genes on the Y chromosome responsible for?
early testes development and relatively high testosterone production, resulting in male reproductive structures
Why does the Y chromosome have fewer loci and therefore carries fewer genes?
because it is significantly smaller than the X chromosome
Why do most of the alleles in the X chromosme have nothing to pair up with?
because it has so many more genes, so a gene whose locus is at an extremity of the X chromosome wouldn’t have a partner from the Y because the Y chromosme doesn’t extend that far from its centromere
What are sex-linked traits?
Any genetic trait that has a gene locus on the X or Y chromosome
What is an example of a sex-linked trait?
haemophilia
What problem does haemophilia cause?
blood not being able to clot properly
What are the alleles for haemophilia always found?
on the X chromosome
What are the possible genotypes for haemophilia?
X^H X^H = non-affected female
X^H X^h = non-affected female who is a carrier
X^h X^h = affected female
X^H Y = non-affected male
X^h Y = affected male
Why is it unlikely for an offspring to inherit any X^h alleles?
because they are rare in most populations of humans worldwide
Why can only females be carriers of haemophilia?
because only females can be heterozygous
What can males not be carriers for?
X-linked alleles
What are pedigree charts used to show in genetics?
How a trait can pass from one generation to the next
What does polygenic inheritance involve?
2 or more genes influencing the expression of one trait
What is continuous for variation?
When an array of possible phenotypes can be produced
What is an example of continuous variation?
Human skin color.
What is the intensity of pigment in our skin the result of?
The interaction of multiple genes
What is discrete variation?
When variation is not continuous
How would an outlier be determined with a box and whisker plot?
Multiply the IQR ( difference between 75th and 25th percentiles) by one point five and add this value to quartile three or subtracted from quartile one
What is part of the law of segregation?
Each gamete will receive only one of the 2 copies that the parent can give
What is the distribution ratio?
9:3:3:1
Why is the distribution ratio what it is?
Because of the movement of chromosomes during meiosis
What is Mendel’s law of independent assortment?
The alleles of two or more different genes get sorted into gametes independently of another
