Download Chapter 8: Cell Division

Study Guide Exam 2 (Chapters 8-11)
Chapter 10: DNA
1. Know all aspects of DNA, including the information it carries and its detailed structure.
2. Know the general process of DNA replication & that it is performed by DNA
polymerase (you will need to compare it to DNA transcription- see chapter 9)
3. Understand the concepts of: semi-conservative replication.
4. Understand leading and lagging strand synthesis in DNA replication (and that lagging
strand synthesis is due to the nature of DNA polymerase in that it only works in the 5’ to
3’ direction).
5. Understand the concept of DNA proofreading and repair during the process of
replication – why is it so important.
6. Realize that DNA replication (DNA synthesis) occurs during the S phase of the cell
cycle.
Chapter 11: Gene Expression
1. Understand the two-step process of protein synthesis (transcription and translation);
also define what a protein is.
2. Know the difference between DNA and RNA.
3. Know the three different types of RNA.
4. Know what codons are and their role in determining the amino acid composition of
proteins; also the concept of start and stop codons. Know AUG is the only start codon,
and that there are 3 stop codons, but don’t memorize the stop codons.
5. Know the details discussed in class regarding transcription (DNA to mRNA) and
translation (mRNA to protein) and where they occur within the cell.
6. Be familiar with the types of gene mutations: substitutions, insertions, and deletions.
7. Be able to distinguish between insignificant, harmful, and beneficial mutations
8. Understand that gene expression is a regulated process and that not all genes are not
expressed in every cell type; depending on the cells physical or temporal environment it
will receive signals that will determine if a particular gene is expressed or not.
Chapter 8: Cell Division
1. Know about the state of DNA compression in non-dividing cells versus in dividing cells
and be able to explain the reason for the state of each.
2. Understand the organization of eukaryotic chromosomes; understand the concept of
homologous chromosomes, and diploid versus haploid chromosome number.
3. There are two types of cell division, mitosis and meiosis. Know what cells undergo each
type of division.
4. Know the steps involved in the cell cycle: mitosis and interphase (see figure).
5. Know the detailed steps of mitosis (PMAT) – division of the nucleus.
6. Know what occurs in cytokinesis – division of the cytoplasm; how is it different in
animal cells versus plant cells?
7. Know the 3 phases of interphase (G1, S, and G2). What occurs in S phase? DNA
replication also known as DNA synthesis. When do cells exit the cell cycle and what
does it signify? Go; the cell is given a signal that it will not undergo another round of cell
division, so it exits the cell cycle during Go. Therefore the single stranded chromosomes
(chromatids) do not replicate during the S phase to produce double stranded
chromosomes.
8. Know the detailed steps of meiosis I and meiosis II (see your handouts and the book for
nice colored pictures).
9. How are mitosis and meiosis different?
10.How does meiosis produce genetic variability? In Prophase I there is crossing over of
homologous chromosomes pairs, and in Metaphase I there is random alignment of the
homologous chromosomes at the equator of the cell.
Chapter 9: Inheritance
1. Who was Gregor Mendel and what did he study?
2. Know the difference between self-fertilization and cross-fertilization.
3. For the extra credit: Understand Gregor Mendel’s experiments described in class for the
mono-hybrid cross for flower color in pea plants:
a. How did he generate true-breeding flowers (purple and white)
b. What where the offspring (F1) when he crossed the true-breeders in the parental
generation (P1)? How do you explain these results?
c. What F2 offspring were produced when he allowed the F1 generation to selffertilize? How do you explain these results?
4. Define & understand:
a. Dominant and recessive alleles
b. Homozygous dominant, homozygous recessive, and heterozygous
c. Genotype and phenotype
5. What are a monohybrid cross and a dihybrid cross?
6. Define the law of segregation in regards to paired alleles of a gene.
7. Define the law of independent assortment in regards to paired alleles that control
different traits.
8. In a dihybrid cross, if the two traits you are studying are on 2 different chromosomes (see
handout):
a. What is the typical phenotypic ratio if you cross two true- breeders? All offspring
are heterozygotes for both traits.
b. What is the phenotypic ratio if you self–fertilize a heterozygote for both traits?
9:3:3:1
c. Extra-credit: know how to set up a dihybrid cross like example in lecture.
9. Just know this fact: In a dihybrid cross, if the two traits you are studying are on the
same chromosome and are genetically linked, then the traits will not assort
independently. The offspring in this case will not a phenotypic ratio as in #10.
10.Understand the concept of genetic linkage: When you study two traits (2 genes) that are
both on the same chromosome- the genes are linked. More importantly, the closer the
physical distance of the two genes, the more tightly they are linked. This is to say that
these 2 traits will tend to be inherited together
11.What are the sex chromosomes versus the autosomal chromosomes? Understand how
sex is determined in mammals and the structural difference between the X and Y
chromosome.
a. Know that the sex chromosomes are one set of chromosomes that determine sex of
an individual; X,X = female and X,Y= male
b. The autosomal chromosomes are the remaining chromosome pairs (22 pairs)
c. X chromosome has 1500 genes versus Y chromosome has 20 genes
12.What are sex-linked traits? Why does a sex-linked trait only require one recessive allele
on the X chromosome of a male to show the phenotype?
13.What are three examples of sex-linked traits/disorders? Baldness, red-green color
blindness and Hemophilia. Review Baldness example from lecture for extra-credit.
14.Know about the variations on the Mendelian theme (see handout for details): Incomplete
dominance (snapdragon flower color), polygenic inheritance (human iris color),
multiple effects of a single gene (SRY gene), and the influence of environment on
gene expression (alcoholism and the Himalayan rabbit). Remember that alcoholism
is also polygenic)
15.What is a pedigree and what can it be used for? See below
16.What is a karyotype? A map of an individual’s chromosomes – in which all the
homologous chromosomes are grouped.
17.Know that most genetic disorders are caused by recessive alleles (need two recessive
alleles to express the disorder). What are examples of genetic disorders that are caused by
recessive alleles? Sickle-cell anemia and albinism (know the generals about sickle-cell
anemia). See below
18.Know that a few genetic disorders are caused by dominant alleles. One mutant -allele is
enough to express a disorder. This is because the protein product produced by the mutant
-allele interferes with the function of the normal one. What are examples of genetic
disorders that are caused by dominant alleles? Huntington’s disease and familial
hypercholesterolemia. See below
19.What is non-disjunction (important to remember that it occurs during meiosis I or II and
results in production of the gametes).
20.What disorders can result from nondisjunction? Distinguish between disorders resulting
from abnormal number of sex chromosomes versus an abnormal number of autosomal
chromosomes. See below:
Non-disjunction - Abnormal number of sex chromosomes
XO Female - short, hormone deficiencies, sterile & lack secondary sex characteristics
(Turners)
XXX Female - tall, fertile, decreased intelligence (Trisomy X)
XXY Male - Mixed secondary sexual characteristics, sterile due to low sperm count
(Klinefelter’s)
XYY Male - Tall, increased testosterone levels, violent, slightly decreased intelligence
Non-disjunction – Abnormal number of autosomal chromosomes
Trisomy 21- 3 copies of autosomal chromosome number 21 (Down Syndrome)
Increased age of mother is the most significant factor
Pedigree analysis: diagram that shows genetic relationships among a set of related individuals
(parents, their offspring, offspring’s spouses, etc… - like a family tree, but record of disease
genotype and phenotype. Careful analysis of such a diagram can reveal if a trait is inherited in a
dominant, recessive, or sex-linked pattern:
Autosomal recessive traits/disorders: 2 recessive alleles to show phenotype/trait: Sickle cell
anemia, albinism
Autosomal dominant disorders: 1 mutant allele and one normal allele to show disease
phenotype: Familial Hypercholesterolemia, and Huntington’s disease
Sex-linked traits/disorders: One recessive allele on a male’s X chromosome (has no
counterpart on males Y chromosome) to show trait/disorder; color-blindness or baldness (traits)
and hemophilia (disorder)