Topic 3 - DNA function and structure
Name the 3 parts of a nucleotide.
Phosphate, deoxyribose sugar, nitrogen base
What do restriction enzymes do?
Cut DNA at specific sequences (molecular scissors)
Mitosis makes how many cells, and are they identical?
Two identical diploid body cells
What cells does meiosis produces?
Gametes (sperm or eggs)
What does heterozygous mean?
One dominant and one recessive allele (Tt). A carrier.
Define diploid and haploid.
Diploid (2n) has two sets of chromosomes.
Haploid (n) has one set.
What is gene therapy?
An experimental technique that repairs or replaces faulty genes in a patient's cells to treat a disease
What happens to chromatin during prophase?
It condenses into visible chromosomes, and the nuclear membrane disappears.
Name 2 mutagens.
X-rays, UV radiation, chemicals in cigarette smoke, hepatitis virus
State Mendel's law of segregation.
Allele pairs separate into different gametes during meiosis.
Write the complementary strand for ATCGGA.
TAGCCT
Give 2 benefits of GMOs.
More nutrition, higher yield, less pesticide use, crops grow in new areas
A cell with 2n = 12 does mitosis, and another cell with 2n = 12 does meiosis. How many chromosomes are in each new cell and the gametes produced?
mitosis = 12 chromosomes
meiosis = 6 chromosomes
An organism has 2n = 16. How many chromosomes are in each gamete?
8 chromosomes
Can a male be a carrier for an X-linked trait? Why?
No. He has only one X, so he either has the trait or doesn't.
Why is DNA replication called semi-conservative?
Each new DNA molecule keeps one original strand and has one new strand.
Put in order:
ligase joins the gene into the plasmid,
bacteria make insulin,
cut the plasmid and gene,
put the plasmid into bacteria.
cut the plasmid and gene,
ligase joins the gene into the plasmid,
put the plasmid into bacteria,
bacteria make insulin
Compare the number of cells produced in mitosis and meiosis.
Mitosis: 2 identical diploid cells.
Meiosis: 4 unique haploid cells.
The DNA triplet CAT mutates to CTT. What is the new amino acid?
Leucine (was histidine)
Pure tall (TT) is crossed with pure short (tt), then two F1 plants are crossed. What is the F2 genotypic ratio?
1 TT : 2 Tt : 1 tt
A DNA sample is 30% adenine. What percent is guanine?
20% (A = T = 30%, so G and C share 40%)
Why do some scientists worry rDNA could create "superbugs"?
Plasmids can transfer between bacteria, so resistance genes could spread to harmful bacteria.
Describe mitosis in order without stage names.
Chromosomes double and condense,
line up at the equator,
separate,
move to opposite poles,
then the cell divides.
An organism has 2n = 10. How many chromosomes are in each cell after meiosis I, and after meiosis II?
5 after meiosis I (still doubled), 5 after meiosis II
A trait skips generations, affects both sexes, and an affected daughter has an unaffected father. Which mode?
Autosomal recessive. An affected daughter with an unaffected father rules out X-linked recessive.