Download Cells, DNA and Genetics

Check Your Understanding
Cells, DNA and Heredity
Name ___________________________________
1.
2.
3.
1.
Name the parts of the cell that are numbered. Then describe the function of each
of these organelles.
a. 1). Nucleus- the nucleus contains the genetic material DNA in the
form of chromatin or chromosomes. It also contains regulatory
proteins and the nucleolus which is the site of ribosme synthesis (RNA
and protein).
b. 2). Mitochondrion- this is a double membrane organelle that is
responsible for ATP synthesis. Glucose is converted to ATP in this
organelle. Often called the powerhouse of the cell.
c. 3) Rough endoplasmic reticulum- a vast system of interconnected,
membranous, infolded, convoluted sacks that are located in the cell’s
cytoplasm and is continuous with the outer nuclear membrane.
Rough ER is covered with ribosomes and is responsible for
transporting materials such as proteins to the Golgi.
2. What is a gene? What ultimately does a gene DO? A gene is a region or
location on a chromosome that codes for a certain trait. A gene ultimately
produces a protein.
3. Describe DNA in terms of the substances used to make it up and its shape. DNA,
known as deoxyribonucleic acid, is made up of phosphate groups, a sugar
(deoxyribose), and 1 of 4 nitrogenous bases, adenine, guanine, cytosine or
thymine. The structure looks like a ladder with phosphate groups and
sugars making up the backbone and the nucleotides base pairing
(complimentary bases) to form the rungs of a ladder. The whole molecule is
then twisted into a structure known as a double helix.
4.
How is DNA organized within a cell nucleus? How many chromosomes do
humans have? How many pairs of chromosomes do humans have? DNA is
organized into chromosomes. We have 23 pairs of chromosomes, which
means we inherited 1 set of chromosomes from our mother and another set
from our father. Pairs of chromosomes contain the same genes, though there
might be slight differences in the genes which will ultimately code for a
slightly different protein, depending on which gene is expresses (moms or
dads).
5.
What does semi-conservative replication mean? That when DNA replicates, it
always results in a new molecule that has 1 old strand and one new strand.
6.
If you had the DNA sequence
5’ ATGGCCGTAGCTAATTAA 3’
3’ TACCGGCATCGATTAATT 5’
What would you wind up with after 1 round of DNA replication?
5’ ATGGCCGTAGCTAATTAA 3’
3’ TACCGGCATCGATTAATT 5’
5’ ATGGCCGTAGCTAATTAA 3’
3’ TACCGGCATCGATTAATT 5’
You would wind up with two identical molecules of DNA that you started with. One
strand will be old and one new (I indicated old strands by bolding).
7. If you took the 3’ to 5’ strand of DNA (bottom strand) and underwent
transcription, what would your resulting RNA be? What KIND of RNA is this
strand.
5’ AUGGCCGUAGCUAAUUAA 3’
Messenger RNA
8.
The RNA leaves the nucleus and goes to what organelle to be translated? What
does it mean to be “translated”. Ribosome. mRNA codes for a set of amino
acids that are linked together to form a protein.
9. Our somatic cells are said to be diploid (in terms of chromosomes). What does
that mean? Our sex cells (gametes) are said to be haploid. What does that mean?
Why are gametes haploid? Diploid cells have PAIRS of chromosomes, one set
from mom, one set from dad. Haploid cells only have 1 pair of chromosomes
so that upon fertilization, the correct number of chromosomes are restored
(in human terms, baby will have 46 chromosomes, if you didn’t half the
number of chromosomes in the gametes, upon fertilization baby would have
92 chromosomes and would no longer be human!)
10. We inherit our chromosomes and genes from our parents. If you mom has brown
eyes (BB) and your dad has blue eyes (bb), what color eyes would you have?
What would be your genotype (the 2 genes you inherited written as BB, Bb, bb).
If you crossed a heterozygous brown eyed person with another heterozygous
brown eyed person, what would be the odds/ratio that their first child would have
blue eyes?*** (difficult question)
B
B
b
Bb
Bb
b
Bb
Bb
So, your phenotype is that you have brown eyes. Your genotype is Bb. So, if you
crossed Bb x Bb you would get this:
B
b
B
BB
Bb
b
Bb
bb
Therefore, the odds of having a blue eyed baby is ¼ or 25%.
11. Now, let’s say this couple had 4 children all with blue eyes. If you did a Chisquare analysis for this situation, would you say that having all blue eyed children
was a result of NORMAL random chance or that something was helping to select
blue eyed children? In other words, your prediction would be that if a couple had
4 children, _____ many would have blue eyes. This is your hypothesis (null
hypothesis for you students with stats background). So.
Blue Eyes
Brown Eyes
Observed (O)
4
0
Expected (E)
1
3
(O-E)
3
-3
(O-E)2/E
3
3
P=
6
The P statistic that you will compare your P value to is 3.841.
a) Do you reject or accept your hypothesis? Why?
Reject the hypothesis that 1 out of 4 children will have blue eyes. So, we might
conclude that something is helping to “select” blue eyed children over brown eyes
because they are being expressed way more often than expected. However, 4 is a
very low sample size, so while the students might buy this, you could never make a
conclusion based upon 4 children 
12. Let’s look at a dihyrbrid cross where 2 traits are being expressed. Let’s say we
are crossing tall plants (T or t) with hairy leaves (H or h). Being tall is dominant
(T) while being short is recessive (t) and having hairy leaves is dominant (H) and
having smooth leaves is recessive (h). I made some crosses in the lab, and have
branched out to a new cross of TTHh crossed with TtHh, as is shown below:
TH
Th
TH
Th
TH
TTHH
TTHh
TTHH
TTHh
Th
TTHh
TThh
TTHh
TThh
tH
TtHH
TtHh
TtHH
TtHh
th
TtHh
Tthh
TtHh
TtHh
Give the phenotypic ratio for the above cross:
Tall: Hairy
Tall: Smooth
Short: Hairy
Short: Smooth
(anyone with a T and an H) so:
(anyone with a T and hh):
(anyone with tt and H);
(anyone with tt and hh)
13
3
0
0
Now give me the Genotypic ratio of the above cross below: List all the possible
genotypes that you see above and then count:
TTHH: 2 which = 2/16 or 1/8
TTHh: 4 which = 4/16 or 1/4
TThh: 2 which = 2/16 or 1/8
TtHH: 2 which = 2/16 or 1/8
TtHh: 5 which = 5/16
Tthh: 1 which = 1/16