Inheritance

Question 1

genetics

Answer 1

branch of the biological sciences
that concerns inheritance of traits (heredity)

Question 2

traits

Answer 2

individual characteristics that can
range from visible to molecular to behavioral

Question 3

genotype

Answer 3

the alleles of individuals
- genotype and environmental conditions can
both influence the phenotype of individuals

Question 4

phenotype

Answer 4

observable traits

Question 5

J. Gregor Mendel

Answer 5

an
Austrian monk who used
experiments with garden
peas to establish rules of
trait inheritance in 1865
- he founded genetics, but his research was ignored until long after his death

Question 6

mendelian genetics

Answer 6

Mendel chose to
use garden peas
for his research.
- inexpensive
- easy to grow
- many seeds
- visible traits
- mate control

Question 7

principle of dominance

Answer 7

purebred peas with round seeds were crossed
with purebred peas with wrinkled seeds, while
hybrid offspring were allowed to self-fertilize

Question 8

monohybrid cross

Answer 8

a breeding experiment between P generation (parental generation) organisms that differ in a single given trait. The P generation organisms are homozygous for the given trait. However, each parent possesses different alleles for that particular trait

Question 9

dominant gene

Answer 9

particular variant of a gene, which for a variety of reasons, expresses itself more strongly all by itself than any other version of the gene which the person is carrying, and, in this case, the recessive
- RR is homozygous dominant (round seeds),
and individuals make gametes with R allele

Question 10

recessive gene

Answer 10

a gene whose effects are masked in the presence of a dominant gene
- rr is homozygous recessive (wrinkled seeds),
and individuals make gametes with r allele

Question 11

principle of segregation

Answer 11

mendel proposed that a parent carries two
of each hereditary factor (gene), and those
factors separate (during meiosis) such that
a gamete will carry only one of the factors.
- uppercase and lowercase letters were used
to represent dominance (RR) and recessiveness (rr)
- Rr is a heterozygote (round seeds due to the
dominance of R alleles), and individuals can
produce gametes that carry the R or r allele

Question 12

probability rules

Answer 12

addition for two mutually exclusive
events (cannot happen at the same time):
- p(A or B) = p(A) + p(B)
- Multiplication rule for two independent
events (one does not influence the other):
- p(A and B) = p(A) × p(B)

Question 13

principle of independent assortment

Answer 13

proposes
that genes affecting different traits are passed
down to offspring independently of each other
- purebred peas with yellow and round seeds
were crossed with purebred peas with green
and wrinkled seeds, while hybrid offspring
of that mating were allowed to self-fertilize

Question 14

heterozygote

Answer 14

Rr is a heterozygote (round seeds due to the
dominance of R alleles), and individuals can
produce gametes that carry the R or r allele
- heterozygotes will express only the dominant
trait according to the principle of dominance

Question 15

incomplete dominance

Answer 15

incomplete dominance is a non-Mendelian
pattern of inheritance where heterozygotes
express a phenotype that is intermediate to
the phenotypes of homozygous individuals

Question 16

codominance

Answer 16

another non-Mendelian inheritance pattern
is codominance, where heterozygotes express
both phenotypes of homozygous individuals
- ABO blood types are an example in humans
- Gene ABO is on chromosome 9 and codes for
an enzyme that attaches different sugars (A,
B, or none) to the surfaces of red blood cells

Question 17

epistasis

Answer 17

an interaction in which one gene
can influence how another gene is expressed
- example is the color of
- labrador retrievers
One gene codes for a protein that is needed
to produce the pigment, and black pigment
(B) is dominant to the chocolate brown (b)
- another gene encodes a protein involved in
depositing the pigment in hair follicles, and
pigment (E) is dominant to no pigment (e)

Question 18

sex-linked traits

Answer 18

reciprocal crosses switch the phenotypes
of male and female parents, and different
results indicate sex is an important factor
- sex-linked inheritance is caused by genes
located on the sex chromosomes (X or Y)
- X and Y symbols are used with uppercase
and lowercase letters to represent alleles

Question 19

multiple allelism

Answer 19

the existence of more
than two alleles for a gene in populations
- similar to our ABO gene, there are three
alleles for a gene on the Z chromosome in
pigeons that affects the color of feathers

Question 20

ZW system

Answer 20

ZW is a genetic sex determination system
used by birds and many other organisms
- males are ZZ and females are ZW, which
is opposite to the XY system in mammals

Question 21

pedigree

Answer 21

pedigrees are family trees that also provide
information about the inheritance of traits

Question 22

quantitative analysis

Answer 22

quantitative traits vary on a continuous scale
in populations rather than fall into categories.
- quantitative traits are influenced by multiple
genes (polygenic) and environmental factors
- height
- metabolic rate
- blood pressure
- hair color

Question 23

extranuclear DNA

Answer 23

mitochondria and chloroplasts contain their
own DNA that is separate from the nucleus.
- human mitochondrial DNA is arranged in a
circle and has only 37 genes, all of which are
essential for normal mitochondrial function.
- mitochondrial DNA is inherited maternally
for most animals, including human lineages