Introduction to Genetics Review (Exam Review #45-58 & #73-94) Flashcards
What is probability?
The likelihood of an event
What is the probability of rolling 2 fours on a die in a row?
1/36
What diagrams are used to show the possible gene combinations that could result from a genetic cross?
Punnett Squares
What are organisms that have 2 identical alleles for the same trait called?
Homozygous
What are organisms that have 2 different alleles for the same trait called?
Heterozygous
What word is used to describe the physical characteristics of a genetic cross?
Phenotype
What word is used to describe the genetic makeup of a genetic cross?
Genotype
Draw a Punnett Square to show a cross between a heterozygous round seed and a wrinkled seed. (Round allele: R, Wrinkled allele: r) Give the possible genotypes and phenotypes and their percentages.
Genotypes:
Rr-50%
rr-50%
Phenotypes:
Round-50%
Wrinkled-50%
Draw a Punnett Square to show a cross between a homozygous purple, heterozygous long-feathered Foo-Foo bird and a pink, short-feathered Foo-Foo bird. (P: purple, p: pink, L: long-feathered, l: short-feathered) Give the possible genotypes and phenotypes and their percentages.
PL Pl PL Pl
pl PpLl Ppll PpLl Ppll
pl PpLl Ppll PpLl Ppll
pl PpLl Ppll PpLl Ppll
pl PpLl Ppll PpLl Ppll
Genotypes:
PpLl-50%
Ppll-50%
Phenotypes:
Purple with long feathers-50%
Purple with short feathers-50%
What is the law of independant assortment?
Alleles assort independently from one another.
What happens in incomplete dominance?
The traits combine.
Give an example of incomplete dominance.
A red flower and a blue flower have purple offspring
What happens in codominance?
Both traits show through.
Give an example of codominance.
A dog with a brown parent and a white parent has spots of both colors.
What are traits that are controlled by two or more genes called?
Polygenic
Genes that have more than two alleles are said to have what?
Multiple alleles
The two chromosomes in a human that determine an individual’s sex are called what?
Sex chromosomes
What is a pedigree?
A chart showing the appearance of a trait in a family
Which pattern(s) of inheritance are consistent with this pedigree?
i. Sex-linked
ii. Complete dominance
iii. Cocominance
Complete dominance
According to this pedigree, what is the best guess of the genotypes of the student’s parents?
Heterozygous
According to the pedigree, what is(are) the most likely genotype(s) of the student’s sister?
WW or Ww
Aside from genetics, what factor plays an important role in a person’s traits?
Environment
What is the allele for Blood-type A?
IA
What is the allele for Blood-type B?
IB
What is the allele for Blood-type AB?
IAIB
What is the allele for Blood-type O?
i
List all the possible genotypes for Type-A blood.
IAIA and IAi
List all the possible genotypes for Type-B blood.
IBIB and IBi
List all the possible genotypes for Type-AB blood.
IAIB
List all the possible genotypes for Type-O blood.
ii
What is the dominant allele of the AB blood groups?
IA and IB
What is the recessive allele of the AB blood groups?
i
What is the dominant allele for the Rh blood group?
Rh+
What is the recessive allele for the Rh blood group?
Rh-
A man heterozygous for type-A blood marries a woman heterozygous for type-B blood. What is the probability as a percentage that their child will have type-O blood?
Hint: Use a Punnett Square
25%
Name a disorder caused by a recessive allele.
Color-Blindness
Name a disorder caused by a dominant allele.
Huntington’s
Name a trait controlled by codominant alleles.
Blood type
In diseases like cystic fibrosis and sickl cell anemia, what causes the disorder?
A change in the DNA
What are sex-linked genes?
Genes on the X or Y chromosome
Give 2 examples of sex-linked disorders in humans.
Color-blindness and hemophilia
In fruit flies, eye color is a sex-linked trait on the X-chromosome. If a female fruit fly heterozygous for red eyes (red eyes are dominant) is crossed with a white-eyed male (white eyes are recessive), what percentage of their offspring will have white eyes?
Hint: use a Punnett Square
50%
(remember that red eyes are XR and white eyes are Xr)
Why do males tend to have a higher probability of getting a sex-linked disorder than females?
They only have one X chromosome, and therefore only have one allele for each X-linked gene. That allele, being the only one, must show through.
What is nondisjunction?
It occurs when homologous chromosomes fail to separate.
Describe 2 chromosomal disorders.
Turner’s: Only 1 X-chromosome
Klinefelter’s: 1 Y and too many X’s
What is DNA fingerprinting used for?
It is used to identify people.
What is the purpose of the human genome project?
To map the human genome
What is gene therapy?
Injecting a “good” gene to replace a “bad” one
What are some ethical issues that can be raised with human genetics?
Answers may vary
