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47 Cards in this Set

  • Front
  • Back

Who is Gregor Mendel?

1. discovers basic principles of heredity

2. breed garden pea plants- foundation of genetics

Why did Mendel work with pea plants?

1. easy to cultivate

2. could self pollinate/ cross pollinate

3. had many varieties

4. had true-breeding varietes (gene. pure)

As a result of Mendel’s experiments, what basic principles did he discover?

He discovered:

1,law of segregation

2. law of independent assortment

What is the law of segregation?

1.Each organism contains two alleles for each inherited character

2. the alleles segregate (separate) during the formation of gametes

3. each gamete contains only one allele for each character

What is the law of independent assortment?

1. Members of one pair of alleles (characters) separate independently of members of another pair of alleles (characters).

2. Therefore all possible combination of alleles (characters) can occur in the gametes.

Define character.

one pair of alleles

Define trait.

Characteristics or attributes of an organism that are expressed by genes

Define true-breeding.

- producing offspring with the same traits (phenotypes) as the parent

- self pollination

- must be homozygous (RR or rr)

Define hybridization.

producing hybrids when mating two varieties

Define monohybrid-cross.

a cross that tracks the inheritance of a single character

ex: flower color

Define P-generation.

True breeding parents

Define F1 generation.

The hybrid offspring of the P gen.

Define F2 generation.

the offspring that is produced when F1 gen. self-pollinates

Define dominant trait.

An inherited trait that results from the expression of the dominant allele over the recessive allele.

ex. RR or Rr

Define recessive trait.

A genetic trait that results from the expression of the two recessive alleles.

ex. rr

Define alleles.

alternative versions of a gene found on homologous chromosomes

Define somatic cells.

all body cells of an organism

Define Punnett square.

1. A tool that helps to show all possible allele combinations of gametes in a cross of parents with known genotypes

2. in order to predict the probability of their offspring possessing certain sets of alleles.

Define homozygous.

when an organism has 2 identical alleles.

ex: RR or rr

Define heterozygous.

When an organism has 2 different alleles

ex: Rr

Define phenotype.

description of an organism

Ex: Tall, purple flower

Define genotype.

the letters that show the genetic makeup

Ex: Tall (hom-dom), Purple (het) flower


Conduct a simple monohybrid-cross using letters to represent alleles.

P gen: TT (T) - tall * tt (t) - short

F1 gen: Tt - tall
: Tt - tall * Tt - tall

F2 gen: 1TT, 2 Tt, 1tt = 3 tall & 1 short

Conduct a test cross.

P gen: Tt (T) - tall * tt (t) - short

F1 gen:

: 2 Tt and 2tt = 2 tall & 2 short

F2 gen: offspring- tt

Why would someone use a test cross?

If there is an organism with a dominant allele and the other allele is not known.

7. Conduct a dihybrid cross.

P gen: TTGG - tall/green * ttgg - short/yellow

P gen gamete: TG * tg

F1 gen: TtGg

F1 gametes: (Tt)(Gg) and (Tt)(Gg) -tall/green

F2 gen: 9 tall/green, 3 tall/yellow, 3 short/green, and 1 short/yellow

What is incomplete dominance? example.

When F1 hybrids are inbetween the the parent phenotypes; F1 hybrids have a hetero. condition

ex. P1: red (RR) * P2: white (rr)

= F1: pink (Rr) 100%

What is complete dominance?

When phenotypes of hetero. and homo. are indistinguishable

What is codominance? example.

When neither allele is dom. over the other.

-both are expressed in hetero.

Ex. AB blood: IaIb unlike A blood: IaIa

Define multiple alleles.

When genes exist within a population in more than 2 allele forms

ABO blood group: 3 forms




Define pleiotropy. example.

When on gene can affect the whole body (characteristics)

ex. sickle cell allele

Define epistasis. example.

I gene that affects another gene in a different location, determintes whether that second gene gets expressed.

Ex. Fur color in mice B-black b-brown,

C-pigment, or c- no pigment; affects whether the mouse will be brown, black, or white (cc)

Define polygenic inheritance. example.

An additive effect of 2+ genes on a single phenotype characteristic

ex. skin pigment: three genes A, B,C- dark pigments and a,b,c- light pigments

= AABBCC (darkest), aabbcc (lightest), AaBbCc (midtone)

What is the chromosomal theory of inheritance?

The chromosomal theory of inheritance holds that the separation of maternal and paternal chromosomes during gamete formation is the physical basis of Mendelian (Henry Mendel) inheritance.

What are X-linked genes?

sex-linked genes that are located in sex chromosomes

What are linked genes?

A gene that is co-transcribed with another, due to proximity on the same chromosome.

What is a gene locus?

location of a gene on a chromosome

What are the sex chromosomes for humans?

XX- female

XY- male

Give some examples of sex-linked genes.

When all female flies have red eyes.

When male flies can have red or white eyes.

What are the Barr Bodies in female mammals?

inactive X chromosome (only 1 X is active, but it will be random)

Define nondisjunction.

members of a pair of homologous chromosomes do not move apart properly during meiosis I or II

- 1 gamete can receive two of the same chromosomes while another receives zero.

Define euploidy.

normal number of chromosomes (46)

Define aneuploidy.

abnormal number of chromosomes

Define trisomy.

3 copies of the chromosome (47)

ex. down syndrome

Define monosomy.

1 copy of the chromosomes

ex. Turner syndrome

Define polyploidy.

more than two complete sets of chromosomes

What is a karyotype?

a size-ordered chart of the chromosomes in a cell