Name: _____________
Date: _______
GENETICS UNIT EXAM STUDY GUIDE
STANDARD 7.2 ENVIRONMENT AND GENES
(pg. 198 in new text, Gattaca Movie Notes)
1.
Are a person’s characteristics decided only by their genes/genotype? Why or why not? If not, WHAT can
also affect a person’s characteristics or phenotype?
Many physical human traits are determined solely by genes. For example, a person’s natural hair color, eye
color, and blood type are all determined by genes.
Other human traits are determined by the interaction of genes and a person’s environment. A person’s
height, for example, is mostly controlled by his or her genes. However, if that person eats unhealthily
during his teenage years he may end up much shorter than predicted by his genes.
Alternatively, traits such as athleticism or musical ability are mostly determined by a person’s
environment (it’s pretty hard to be a pro-football player if you have never played football before!) but
there are genetic influences involved as well. For example, Michael Phelps is said to have a body structure
that is well adapted to the sport of swimming (tall and lean with big hands and feet like flippers!).
In conclusion, the environment can influence a person’s phenotype or physical characteristics—but only to
an extent. It is important to remember that no matter how hard you try—you cannot actually change your
genes/genotype. For example, a person with a genotype that predicts a short phenotype will never grow to
be 6’10” no matter how much milk he drinks!
2. A person’s ENVIRONMENT can affect his or her phenotype but not his or her genotype.
STANDARD 7.2A ASEXUAL VS. SEXUAL REPRODUCTION
(Genetics Week 1 Notes)
3. What is the difference between sexual and asexual reproduction?
In sexual reproduction, genetic material from two parents combines to produce a new organism which
differs from both parents. In asexual reproduction, only 1 parent is involved and the offspring is identical
to the parent genetically.
4. Define haploid, then give two examples of haploid cells.
These are cells with half the number of usual chromosomes for an organism (only 1 set of genetic
instructions for each trait). The ONLY two examples of haploid cells are egg cells and sperm cells.
5. Define diploid, then give two examples of diploid cells.
A diploid cell contains two sets of chromosomes, one set from each parent. Any body or somatic cell can
be used as an example of a diploid cell (i.e. heart cell, liver cell, muscle cell, neuron, skin cell etc.)
STANDARD 7.2B CHROMOSOMES and INHERITANCE
(pg. 170-174 in textbook, Meiosis Notes and Sexual Reproduction notes)
6. What is the chromosome theory of inheritance?
46According to the chromosome theory of inheritance, genes are carried from parents to offspring on
chromosomes.
7. In sexual reproduction, offspring inherit half or 50% its DNA from one parent and half or 50% its DNA
from another parent.
8. Humans have 23 chromosomes in each of its sex cells.
9. Humans have 46 chromosomes in a normal body cell.
10. Humans have 23 pairs of chromosomes in normal body cells.
11. Fill in the blanks for meiosis:
1. Every chromosome in the cell is COPIED.
2. The chromosome pairs line up next to each other in the CENTER of the cell.
3. The chromosome pairs then SEPERATE from each other and move to opposite ends of the cell.
4. The cell divides—and TWO CELLS FORM form, each with half the number of chromosomes.
5. The chromosomes move to the MIDDLE of the cell.
6. The centromeres split and the CHROMATIDS separate.
7. The cells divide—4 SEX CELLS are produced after this division.
12. What is the product of meiosis? How is this different from mitosis?
4 sex cells are produced with half the amount of DNA/chromosomes as the parent cell.
13. A butterfly skin cell has 16 chromosomes.
1. How many chromosomes will its egg cells have after meiosis? 8
2. How many chromosomes will a butterfly cell have after mitosis? 16
14. What are chromosomes made up of?
Chromosomes are made up of coiled up chromatin which is in fact coiled up DNA. Sections of this DNA
that code for a specific trait are called genes. Thus, we can say that chromosomes are made up of many
genes joined together like beads on a string.
15. If the sex cells of a woman carry a mixture of B alleles and b alleles. What is the woman’s genotype for
Gene B? Bb
16. If the sex cells of a man carry only c alleles, what is his genotype? cc
STANDARD 7.2C INHERITANCE PATTERNS
(pg. 192-197, Inheritance Patterns Notes)
17. What are the three inheritance patterns in humans?
1. Single Gene with 2 alleles
2. Single gene with multiple alleles
3. Traits controlled by many genes
18. What does the term multiple alleles mean?
Some human traits are said to be controlled by a single gene that has more than two alleles. Such a gene is
said to have multiple alleles—three or more forms of a gene that code for a single trait.
19. The gene for Widow’s peak has only 2 (number) alleles. That’s why we only see 2 (number) phenotypes:
Widow’s Peak and No Widow’s peak.
20. Which inheritance pattern determines height? How do you know? What other human traits are
determined by this inheritance pattern?
Height is a trait that is controlled by many genes working together. We know this because height shows a
large variety of phenotypes. At least 4 genes control height in humans so there are many possible
combinations. Skin color is another human trait that is determined by this inheritance pattern.
21. If a baby has two X Chromosomes, the baby will be a GIRL
22. If a baby has an X and a Y Chromosome, the baby will be a BOY
STANDARD 7.2D MENDEL and PUNNETT SQUARES
(pg. 154-167, A, B, P’s of Life, Dominant vs. Recessive Alleles, Punnett Squares)
__e___
1.
__g___
2. Trait
b.
___i__
3. Alleles
c.
4. Gene
5. Dominant Allele
6. Recessive Allele
d.
e.
f.
_____
7. F1 Generation
g.
___a__
8. F2 Generation
h.
__b___
___d__
9. Purebred
10. Hybrid
i.
j.
___k__
11. Heterozygous
k.
___o__
___l__
12. Homozygous
13. Phenotype
l.
m.
___n__
14. Genotype
n.
__j___
15. Codominance
o.
___m__
___f__
__c___
Heredity
a.
In Mendel’s pea plant experiments, this generation had a ratio of
3 tall plants to 1 short plant.
The offspring of many generations that have the same trait. (HH
or gg are examples)
An allele that is hidden whenever the other type of allele is
present. We use a lower case letter to show this type of allele.
An organism that has two different alleles for a trait.
The passing of physical characteristics from parent to offspring.
An allele whose trait always shows up in an organism whenever it
is present. We use a capital letter to show this type of allele.
Each different form of a characteristic, such as stem height or
seed color.
In Mendel’s pea plant experiments, this generation had all tall
plants.
The different forms of a gene. Such as B or b.
In this pattern of inheritance, the alleles are neither dominant
nor recessive. As a result, both alleles are expressed in the
offspring.
An organism that has two different alleles for a trait. Examples:
Bb, Tt, yY
An organism’s physical appearance or visible traits.
The factors that control a trait. Also, defined as sections of
DNA that code for one protein.
An organism’s genetic make-up or allele combinations—the
“LETTERS”
An organism that is said to have two identical alleles for a trait.
Examples include: GG, tt, BB
23. What is a punnett square?
A punnett square is a chart that shows all of the possible combinations of alleles that can result from a
genetic cross.
24. SpongeBob’s aunt and uncle, SpongeWilma and SpongeWilbur, have the biggest round eyes in the family.
Wilma is believed to be heterozygous for her round eye shape, while Wilbur’s family brags that they are a
pure line.
1. Give the genotype for each person. Wilma – Rr Wilbur -RR
2. Complete the Punnett square to show the possibilities that would result if they had children.
3. List the possible genotypes and phenotypes for the kids.
Genotypes: RR or Rr ; Phenotypes: Round eyes
4. What is the probability that the kids would have round eyes? 100%
5. What is the probability that the kids would be oval eyes? 0%
Use the information for SpongeBob’s traits
to write the phenotype (physical appearance)
for each item.
25. LL-Long nose
26. Rr-Round eyes
RR
RR
Rr
Rr
TRAIT
Body Shape
DOMINANT GENE
Squarepants (S)
RECESSIVE GENE
Roundpants (s)
Body Color
Yellow (Y)
Blue (y)
Eye Shape
Round (R)
Oval (r)
Nose Style
Long (L)
Stubby (l)
Use the information to write the genotype (or
genotypes) for each trait.
27. Yellow body -Yy or YY
28. Stubby nose - ll
Determine the genotypes for each using the
information in the chart.
29. Heterozygous round eyes -Rr
30. Homozygous long nose - LL
31. Purebred squarepants - SS
32. Hybrid yellow body - Yy
STANDARD 7.2E The GENETIC CODE and MUTATIONS
(pg. 175-176 and pg 180; Genetic Code Notes and Mutation Notes)
33. How is the order of bases a code for life? What exactly does it code for?
Every 3 bases codes for an amino acid in a protein. The order of bases thus determine the order of amino
acids in a protein. The order of amino acids in a protein and the quantity of amino acids in a protein will
determine the type of protein produced.
34. The building blocks of proteins are AMINO ACIDS
35. The order of DNA bases on a gene determine how a PROTEIN is built.
36. 3 (a number) bases code for an amino acid.
37. What is a mutation? What are the two types of mutations?
A mutation is any change in a gene or chromosome. Mutations can cause a cell to produce an incorrect
protein during protein synthesis. As a result, the organism’s trait, or phenotype, may be different from
what it normally would have been. Mutations can occur at the DNA base level (i.e. one base is deleted or
substituted for another) or at a chromosomal level (i.e. incorrect meiosis results in an extra chromosome).