Genetics Part 2 Flashcards
What is a law of hereditary?
a rule for hereditary, it describes how certain traits are passed on
How were the laws of heredity discovered?
using the pea plant
Who used pea plants to discover the laws of heredity?
Gregor Mendel
What type of characteristics in pea plants made mendelian genetics possible?
Either - or traits. The character can be one thing or another
What are the either-or traits in pea plants that Gregor Mendel used?
- flower colour
- seed colour
- seed shape
- pod colour
- stem length
What are the traits of flower colours in pea plants. Which one is dominant? Which one is recessive?
dominant - purple
recessive - white
What are the traits of seed colours in pea plants. Which one is dominant? Which one is recessive?
dominant - yellow
recessive - green
What are the traits of seed shapes in pea plants. Which one is dominant? Which one is recessive?
dominant - round
recessive - wrinkled
What are the traits of pod colour in pea plants. Which one is dominant? Which one is recessive?
dominant - yellow
recessive - green
What are the traits of stem length in pea plants. Which one is dominant? Which one is recessive?
dominant - tall
recessive - short
character or characteristic definition
a heritable feature, such as flower colour, varies between individual plants
trait definition
each variant for a character, such as purple vs white flower (an example of a characteristic)
genotype definition
an organism’s genetic makeup (the pea plant could have FF or Ff)
phenotype definition
an organism’s appearance (the pea plant appears to have purple flowers)
heterozygous definition
an organism that has two different alleles for a character
homozygous definition
an organism that has a pair of identical alleles for a character.
What is the Law of Segregation?
States that inherited traits are determined by pairs of genes and that each of the genes separates into seperate gametes
Only one of the two gene copies present in an organism is distributed to each gamete, the allocation of the gene copies is random in the offspring.
What are Mendel’s Laws?
The law of segregation and the law of independent assortment
What is the Law of Independent Assortment
It states that inheritance of one trait does not affect the inheritance of alleles for another trait.
Incomplete Dominance
When the trait is a mixture of the two parental traits ( one parent has red flowers and other has white, the result is a pink flower in snap dragons)
When does incomplete dominance occur?
when 2 alleles are equally dominant and the heterozygous individuals produce a new phenotype
Codominance
both alleles are expressed at the same time. One allele cannot restrict the other allele
dominant allele
the allele that is fully expressed in the organism’s appearance
recessive allele
has no noticeable effect on the organism’s appearance
what type of letter do you use for a dominant allele vs a recessive allele?
dominant - capital letter
recessive - lower case
Punnet Square
an organized way of showing the possible results of a cross between the gametes of two individuals
Monohybrid Cross
a cross that involves only one allele pair with different traits
dihybrid crosses
when phenotypes and genotypes with two independent alleles are analyzed
Linked genes
genes that are on the same chromosome and that tend to be inherited together
a linkage
all of the genes on one chromosome because they tend to be inherited together
Are linked genes predictable?
Yes. Scientists have discovered that alleles for a given pair of linked genes will separate with a predictable frequency and this frequency is different for different pairs of linked genes
What does the frequency of linked genes depend on?
on how close the alleles of the linked gene are positioned on a chromosome
Where does crossing over occur more frequently?
it occurs more frequently between alleles that are far apart on the chromosome than between alleles that are close together.
What is chromosome mapping?
the process of determining the relative locations of genes on chromosomes - this is only useful in species that reproduce rapidly and produce many offspring
X and Y chromosomes on their homologous DNA
they have very little of it even though they are paired together - in humans, they only have a few genes in common
How many genes is the human X chromosome expected to contain?
about 2000
How many genes is the human Y chromosome expected to contain?
fewer than 100
What are the most important genes?
the sex determination genes
how many copies of all X genes do females have?
2
how many copies of all X genes do males have?
1
what is the frequency of X linked genes vs Y linked genes
many for X-linked, but few for Y linked
What is the inheritance pattern for Red-green colour vision deficiency?
X-linked recessive
What is red-green colour vision deficiency?
when someone cannot distinguish between certain shades of red and green
What is the inheritance pattern for Duchenne muscular dystrophy?
X-linked recessive
What is Duchenne muscular dystrophy?
progressive weakening and loss of coordination
What is the inheritance pattern for hemophilia
X-linked recessive
What is hemophilia?
cannot produce a necessary blood clotting factor
What is the inheritance pattern for X-linked hypophosphatemia
X-linked dominant
What is X-linked hypophosphatemia
softening of bone which leads to bone deformity
What is the inheritance pattern of hairy ears?
Y-linked
What is hairy ears?
hair grow on the outside of ears
how was hemophilia reffered to?
the royal disease because it spread among the royal families in Europe through the descendants of Great Britain’s Queen Victoria
Barr bodies
one X chromosome in each cell in females becomes completely inactivated during embryonic development which then condenses into a compact object called a Barr body
What is the selection of the X chromosome that will form the Barr body?
random and independent in each embryonic cell
Multiple alleles
more than two forms of a gene control the expression of a trait
ow many possible alleles control blood types?
3:
- A (Dominant to O and codominant with B)
- B (Dominant to O and codominant with A)
- O (Recessive to A and B)
Who can type A donate to?
A and AB
Who can type A receive from?
A and O
Who can type B donate to?
B and AB
Who can type B receive from?
type B and O
Who can type AB donate to?
type AB
Who can Type AB receive from?
type A, B, AB and O
Who can type O donate to?
type A, B, AB, O
Who can type O receive from?
type O
What is the dominance in rabbits?
agouti > chinchilla > himalayan > albino
what is the agouti letter
C
what is the chinchilla letter?
C (superscript: ch)
What is the himalayan letter
C (superscript h)
what is the albino letter?
c (superscript a)
Polygenic Trait
a trait in which the phenotype is controlled by two or more genes at different locations (loci) on different chromosomes
What are the three types of fingerprints?
Arch, loop and whorl
lethal alleles
gene combination that causes death - in humans: usually before they can reproduce, it is a major cause of miscarriages and stillbirths
epistasis
genes on one loci mask the genes on a 2nd loci (gene on chromosome 1 can affect the expression of a gene on chromosome 2)
example of epistasis
gene for hairlessness will mask the gene for hair colour
what is a pedigree chart and what is it’s purpose?
pedigree charts show a record of the family of an individual. They can be used to study the transmission of a hereditary condition
what is the symbol for a normal male in a pedigree chart?
white square
what is the symbol for an affected male in a pedigree chart?
black, filled in square
what is the symbol for a normal female in a pedigree chart?
white circle
what is the symbol for an affected female in a pedigree chart?
black, filled in circle
how are generations labelled?
roman numerals
how are people numbered in each generation?
by a number, left to right
