Download in non sex cells

Genetics Review and
Questions
Living Environment
Mrs. Paparella
Spring 2009
DNA provides the set of coded instructions required by every
organism for specifying its traits. The DNA molecule also
provides for a reliable way for parents to pass their genetic
code from one generation to the next. Heredity refers to this
passage of these instructions from one generation to another.
Gene-Chromosome Model
Hereditary information is contained in genes, which are
composed of DNA, located in the chromosomes of each cell.
Chromosomes are found in the nucleus of each cell.
Each gene carries a separate piece of information. An inherited
trait of an individual can be determined by one genes, but is
usually determined by the interaction of many different genes.
A single gene can influence more than one trait. A human cell
contains many thousands of different genes coding for many
different traits.
• Independent assortment is the principle
that states that genes located on different
homologous chromosomes will be
distributed independently of each other.
This allows for greater variety in the
offspring.
• Changes in the sequence of the DNA molecule and
therefore the gene are called mutations. A mutation
may change the manner in which a trait is expressed
by an organism.
• Mutations which occur in non sex cells of sexually
reproducing organisms will not be passed on to the
offspring, although they may result in disease or death
for the organism involved. One possible consequence
of a mutation in a non sex cell is uncontrolled mitotic
cell division or cancer.
• Mutations which occur in sex cells or gametes may be
passed to the offspring. Along with crossing over and
genetic recombination, mutation provides for a source
of variation in sexually reproducing individuals.
•
DNA-> mRNA in nucleus
mRNA then leaves the nucleus
RNA
DNA codes for the formation of RNA in the nucleus of the
cell. RNA is short for another kind of nucleic acid called
ribonucleic acid.
RNA is very similar in structure to DNA except for three
small differences:
a. RNA is a single stranded molecule,
b.RNA lacks the base thymine (T) as it is replaced by
the base uracil (U),
c. its five carbon sugar is ribose ,not deoxyribose
• Three different types of RNA exist: mRNA or messenger
RNA, tRNA or transfer RNA, and rRNA or ribosomal RNA.
One of the primary jobs of DNA is to
Direct Protein Synthesis
• Cells store and use coded information.
The genetic information stored in DNA is
used to direct the synthesis of the
thousands of proteins that each cell
requires. The chemical and structural
properties of DNA are the basis for how
the genetic information that underlies
heredity. DNA is encoded in the sequence
of nitrogenous bases which directs the
formation of proteins in the cell.
Transcription-- Translation
•
First, the DNA code is copied on to the mRNA (messenger RNA) codon. A codon is a
sequence of three nitrogenous bases. This process is called transcription.
•
This mRNA codon is then carried from the nucleus out to the ribosome.
•
Messenger RNA attaches to another kind of RNA called tRNA (transfer RNA).
•
Transfer RNA attaches to amino acids and carries them to the ribosome
located in the cytoplasm of the cell. Ribosomes may be on the Rough ER or
free in the cytoplasm.
•
This assembly of amino acids due to the code provided to RNA by the original
DNA molecule is what produces proteins for the cell.
•
Translation is the production of proteins by decoding mRNA produced in
transcription. Translation occurs in the cytoplasm where the ribosomes are
located. Ribosomes are made of a small and large subunit which surrounds the
mRNA.
•
Remember a protein is a long molecule formed from amino acid subunits.
1.The gene-chromosome theory states that genes
are segments of DNA located on chromosomes
and are found in homologous pairs.
Which figure below would represent the theory?
2.A molecule of DNA is a polymer composed of
which of the following??
A. glucose
B. amino acids
C. fatty acids
D. nucleotides
3. The presence of DNA is important for cellular
metabolic activities because DNA
A. directs the production of enzymes
B. is a structural component of cell walls
C. directly increases the solubility of nutrients
D. is the major component of cytoplasm
•
4. Which nitrogenous bases make up DNA
nucleotides?
A. adenine, thymine, guanine, and cytosine
B. adenine, uracil, guanine and cytosine
C. adenine, thymine, uracil, and cytosine
D. adenine, thymine, guanine, and uracil
5. In squirrels, the gene for gray fur (G) is dominant over
the gene for black fur (g).
If 50% of a large litter of squirrels are gray, the parental
cross that produced this litter was most likely
1. GG x Gg
2. GG x GG
3. Gg x gg
4. gg x gg
6. Which cross could produce a child with type O blood?
1.
AO x BB
2.
AA x BO
3.
AB x OO
4.
AO x BO
7. Which diagram most correctly
represents the process of mitosis?
8.
.
Which represents the genotype of a homozygous
condition?
1. Bb
2. BC
3. bb
4. bc
9. Geneticists have observed that fruit flies that commonly
inherit vestigial wings also inherit lobed eyes. Observations
such as this have helped to develop the genetic concept
known as
1.
segregation
2.
dominance
3.
gene linkage
4.
crossing-over
10. Chromosomes normally occur as
homologous pairs in
1. a sperm cell
2. an egg cell
3. a zygote
4. a gamete
11. Because the gene for hemophilia is located on the Xchromosome, it is normally impossible for a
1. carrier mother to pass the gene to her son
2. hemophiliac father to pass the gene on to his son
3. hemophiliac father to pass the gene to his
daughter
4. carrier mother to pass the gene to her daughter
12. A man with a blood genotype AO marries a woman
with a blood genotype of AO. What blood types could
be expected in their children?
1. type A, only
2. type O, only
3. both type A and type O
4. neither type A nor type O
13. When many hybrid tall pea plants are crosspollinated, the offspring produced will probably be
1. 100% homozygous tall
2. 100% heterozygous tall
3. 50% homozygous tall
4. 50% heterozygous tall
14. A hybrid black-coated guinea pig produces two million sperm
cells. Approximately what number of its sperm cells contain
the recessive gene for white coat color?
1.
1 million
2.
2 million
3.
0
4.
0.5 million
• 15.
Some individuals with blood group A may inherit the genes
for blond hair, while other individuals with blood group A
may inherit the genes for brown hair. This can be explained
by the principle of
1.
dominance
2.
multiple alleles
3.
independent assortment
4.
incomplete dominance
16. The outward appearance (gene expression) of a particular
trait in an organism is referred to as
1.
a genotype
2.
a phenotype
3.
an allele
4.
a chromosome