Genetics - Chapter 5

Question 1

Gregor Mendel

Answer 1

austrian monk
considered the father of genetics
used pea plants to study genetics, heredity, and variation
pea plant grows easily and quickly, it has seven traits that are easily identified, and it is easy to manipulate

Question 2

7 traits of the pea plant

Answer 2

seed shape
seed colour
flower colour
pod shape
pod colour
flower position
stem height

Question 3

Allele
True breeding
Hybrids
Phenotype
Geneotype

Answer 3

allele = alternate forms of a gene
true breeding = individuals that only contain one variation of a trait and can therefore only pass this one variation on to future generations (homozygous)
hybrids = individuals that contain more than one variation of a trait and can therefore pass on more than one variation to future generations (heterozygous)
phenotype = the appearance of traits in an organism
genotype = the specific genes that an organism has

Question 4

Law of segregation

Answer 4

law of segregation = when any individual produces gametes, the copies of a gene separate so that each gamete receives only one copy of a gene and therefore only one allele for all possible traits

Question 5

Monohybrid crosses

Answer 5

determining one trait
one trait will be dominant while the other is recessive
the same letter is used to represent the alleles, the dominant allele is expressed with a capital letter and the recessive allele is expressed with a lowercase letter
can be sex-linked or autosomal

Question 6

Sex-linked inheritance

Answer 6

some traits are located on the sex chromosomes, so the inheritance of these traits depends on the sex of the parent carrying the trait
most known sex-linked traits are X-linked
carrier = female who is heterozygous for the X-linked trait

Question 7

Sex-linked disorders

Answer 7

most sex-linked traits are recessive
males are more susceptible as they only inherit one X, no other X to mask it
examples = red/green colour vision deficiency, hemophilia

Question 8

Hemophilia

Answer 8

condition that affects body’s ability to produces proteins involved in blood clotting
X-linked recessive
causes uncontrolled bleeding

Question 9

Test crosses

Answer 9

when geneticists want to know if an individual is heterozygous or homozygous
cross between unknown genotype and homozygous recessive individual
if any recessive traits are expressed, then the unknown genotype will be heterozygous, if not then the unknown genotype will be homozygous dominant

Question 10

Beyond Mendel’s laws

Answer 10

Mendel studied traits that were purely dominant or recessive and, unfortunately, in nature there exists more than simply two choices for some traits
examples = snapdragons, peppers

Question 11

Incomplete dominance

Answer 11

neither trait is dominant or recessive
a heterozygous individual is a blend of the two traits
instead of using a capital and a lowercase letter, two different letters are used

Question 12

Co-dominance

Answer 12

both alleles for a trait are dominant

a heterozygous individual produces both traits, and is therefore spotted/barred

Question 13

Blood types

Answer 13

a human blood type is a group of red blood cells that have the same antigen markers on the cell surface
antigen = substance that induces the formation of antibodies
in humans a single gene controls a person’s blood type
there are three alleles = A, B, and O
blood types = A, B, AB, and O
types A and B are codominant, and are dominant over type O alleles

Question 14

Antibodies of blood types

Answer 14

type A produces antibodies against type B antigens
type B produces antibodies against type A antigens
type AB produces no antibodies
type O produces antibodies against type A and B antigens
AB = universal recipient
O = universal donor

Question 15

Pedigrees

Answer 15

pedigree = genetic family tree that shows trait prevalence in a family through generations
often used to track the expression of genetic conditions and disorders

Question 16

Autosomal dominant inheritance

Answer 16

autosomal = not on the sex chromosomes
every affected person should have at least one affected parent
shows up in every generation
males and females should be equally affected
two affected individuals may have unaffected children
examples = progena, huntington’s disease

Question 17

Autosomal recessive inheritance

Answer 17

two recessive alleles result in a trait being expressed
an affected person may not have affected parents
can appear to skip a generation
affects both sexes equally
two affected parents will have affected children 100% of the time
examples = albinism, Tay Sachs, Cystic Fibrosis

Question 18

X-linked recessive inheritance

Answer 18

no father to son transmission
predominantly males are affected, affected females are extremely rare
trait appears to skip generations

Question 19

Dihybrid crosses

Answer 19

involves a study of inheritance patterns for organisms differing in two traits
Mendel invented it to determine if different traits of pea plants were inherited independently or dependently during formation of gametes

Question 20

Law of independent assortment

Answer 20

if genes are on separate chromosomes, they are inherited independently of each other
allele pairs separate independently during formation of gametes
likelihood of one allele combination is equal to that of any other pairing

Question 21

Probability

Answer 21

number of times the event occurred divided by number of potential times the event could have occurred
chance is always the same
the probability of independent events occurring together is the product of the probabilities of the independent events