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Common Assessment Review- Quarter 3
Mitosis and Meiosis
1. What are the differences between mitosis and meiosis? How many chromosomes are
in the resulting cells at the end of Meiosis? How about Mitosis?
Mitosis- 2n cells (diploid) produce 2n cells
- produces somatic cells
- produces 2 diploid cells
- Ex: produces skin cells
Meiosis- 2n cells (diploid) produce n cells (haploid)
- produces gametes
- produces 4 haploid cells
- Ex: produces sperm cells
2. Define somatic cell and gametes.
Somatic cell- human body cells, in humans: 46 chromosomes (diploid)
Gamete- sperm or egg cell, in humans: 23 chromosomes (haploid)
Genetics
1. Complete a punnett square cross between an organism that is heterozygous for a trait
and an organism that is homozygous dominant. (Use the letter R to represent your trait;
remember this is only a cross for one trait!)
R
r
R
RR
R
RR
Rr
Rr
2. Complete a punnett square for TWO traits in which one organism is heterozygous for
both traits and one organism is homozygous recessive for both. Let the letter R
represent the first trait and the letter A represent the second trait. RrAa x rraa
RA
Ra
rA
ra
RrAa
Rraa
rrAa
ra
RrAa
Rraa
rrAa
ra
RrAa
Rraa
rrAa
ra
RrAa
Rraa
rrAa
ra
rraa
3. What is the phenotypic ratio of offspring that ALWAYS results after a cross between
heterozygotes individuals? Why?
Shows the dominant allele
3:1
R
R
RR
r
Rr
r
Rr
rr
4. Define heterozygous and homozygous. Also define dominant and recessive.
heterozygous- An organism with two different alleles for a particular trait
homozygous- An organism with two of the same alleles for a particular trait
dominant- One trait dominates or hides the other trait in a heterozygous
organism. Use a capital letter to represent the dominant trait and a lower
case letter to represent the recessive (hidden) trait. Ex. T = tall and t =
short. T is dominant so it will be expressed if it is present
5. Show how 2 Blood type A parents could produce a type O child.
IA
i
IA
IA IA
IAi
i
IAi
Type O
ii
Protein Synthesis
1. What is a nucleotide? What three parts make up a nucleotide?
Nucleotide- subunit of nucleic acid. Composed of a nitrogenous base, 5-carbon
sugar, and a phosphate group
2. What is the order of steps in protein synthesis (known as the central dogma of
biology)? Define replication, transcription and translation.
Replication
transcription
translation
Replication- Parental strands of DNA separate, serve as templates, and produce
DNA molecules that have one strand of parental DNA and one strand of new
DNA. An enzyme, DNA helicase, is responsible for unwinding and unzipping
the double helix.
Transcription- process by which RNA is made. Part of the nucleotide sequence of a
DNA molecule is copied into RNA. Occurs in the nucleus
Steps: DNA is unzipped in the nucleus by an enzyme
- Another enzyme, RNA polymerase, bonds “free nucleotides” to the
exposed bases
- Adenine bonds with uracil (A to U) and guanine bonds to cytosine. This
chain is called mRNA
Translation- nucleotides in mRNA are decoded into a sequence of amino acids in a
protein. Occurs after transcription in the cytoplasm. Involves the ribosomes
Steps: mRNA leaves the nucleus and attaches to the ribosomes, where it acts as
a pattern to line up amino acids
- Each triplet codon codes for an amino acid
- The ribosome reads each triplet codon (on the mRNA)
- In DNA: A bonds with T
C bonds with G
- In RNA: A bonds with U
C bonds with G
3. How many bases make up a codon? How many bases make up an anticodon?
Three bases make up both.
4. Describe the shape of the DNA molecule. What types of bonds hold the bases
together? Draw a small picture. Be sure to include bases, phosphate groups and sugars.
DNA is in the shape of a double helix. Hydrogen bonds hold the bases together.
5. What were the two laws of Gregor Mendel? Describe and define both of them.
Law of Independent Assortment- Random distribution of alleles occurs during
gamete formation. Genes on separate chromosomes sort independently
during meiosis. Each allele combination is equally likely to occur.
Law of Segregation- Two alleles for each trait separate during meiosis.
During fertilization, two alleles for that trait unite.
6. What is a mutation? Be sure to know the differences between some of the main types
of mutations!
A mutation is a change in genetic material.
- Substitution- one base is replaced by another. Usually only one amino acid is
affected.
- Insertion- A frameshift mutation. One or more base pairs is added to the
sequence. Changes the entire amino acid sequence from that point
forward.
- Deletion- A frameshift mutation. One or more base pairs is deleted from a
sequence. Changes the entire amino acid sequence from that point
forward.
Transcription Translation or Replication…
a. DNA Nucleotides bond to one side of unzipped DNA _____replication________
b. RNA Nucleotides bond to both side of unzipped DNA ____transcription_____
c. Involves tRNA ____translation________
d. RNA gets built using DNA Information _____transcription____
e. Protein gets built ____translation____
f.
Happens at the ribosome __translation____
DO NOT FORGET HOW TO USE THE DECODERS! YOU SHOULD KNOW HOW TO
TRANSLATE AND TRANSCRIBE DNA TO PROTEIN!