Flashcards in Exam III Deck (82):
What is recombinant DNA?
DNA built from two sources
What is the purpose of performing a Polymerase Chain Reaction? What are the three steps of a PCR?
1. DNA gets heated until the strands split (Denature)
2. Primers anneal to complementary matches on the target DNA sequence (Anneal)
3. Primers extend the strands (Extend)
Repeated cycles of heating and cooling to make many copies of a specific region of DNA.
What are restriction sites?
The specific nucleotide sequence (short and specific) that the genetic engineering is focused on (i.e. restricted to)
What are restriction enzymes?
Restriction enzymes find the restriction sites on the DNA and cut the DNA up into restriction fragments.
In genetic engineering, restriction enzymes are used to cut DNA molecules within short, specific nucleotide sequences (restriction sites), yielding a set of double-stranded restriction fragments with single-stranded sticky ends.
What are restriction fragments?
The pieces of DNA that are cut and have sticky ends sticking out (double-stranded DNA fragment with single-stranded sticky ends)
"Somatic cells" include all human cells except which kind?
Reproductive cells (sperm or ova) ("gametes")
What are gametes?
Reproductive cells (sperm or ova)
How many chromosomes does each human gamete have?
In what state does chromatin spend most of its time?
In long strands, not wrapped up as chromosomes. It only forms chromosomes in preparation for cell division.
What are sister chromatids?
They are the two halves of the chromosome that form the "X." They are connected along their whole length by sister chromatid cohesion.
Where on the chromosome is the centromere located?
It's the "waist" of the chromosome
What is sister chromatid cohesion?
Sister chromatids stick together along their lengths to form the "X" of a chromosome
What part of the chromosome is the arm? How many arms does one uncondensed, unduplicated chromosome have?
The part of a chromatid to either side of the centromere. Each uncondensed unduplicated chromosome has 2 arms.
What is mitosis?
The division of the genetic material in the nucleus. Usually followed immediately by cytokinesis.
What is cytokenesis?
The division of the cytoplasm (in cell division). Last step in how 1 cell splits to become 2.
What is meiosis?
Cell division that makes gametes, which have only one set of chromosomes (23 chromosomes, rather than 23 pairs of chromosomes)
What parts of cell division does the mitotic (M) phase include?
Mitosis and cytokinesis
What is the phase of cell division that alternates with M phase?
What phases are a part of interphase?
G1 phase (first gap)
S phase (synthesis)
G2 phase (second gap)
["Gap" is a misnomer - cells continue to grow - no gap in growth]
During what phase of cell division does duplication of the chromosomes occur?
S phase (synthesis phase)
What are the 5 stages of mitosis?
What happens during prophase?
Chromatin fibers coil more tightly, condensing into discrete chromosomes. Nucleoli disappear. Mitotic spindle begins to form, and the growth of the microtubules pushes the centrosomes away from each other in the cell.
What happens during prometaphase?
Nuclear envelope breaks up, so microtubules can invade the nuclear area.
Chromatids get pushed and pulled around.
Kinetochore forms (specialized protein structure at the centromere).
What happens during metaphase?
Centrosomes are now at opposite poles of cell. All chromosomes are lined up at metaphase plate in the middle.
What happens during anaphase?
Sister chromatids split and microtubules reel them in to opposite ends of the cell. Each chromatid splits from its sister and becomes its own fully-fledged chromosome.
What happens during telophase?
Spindle apparatus falls apart
Nuclear envelope is re-formed
The cell ends up with 2 nuclei
Telophase overlaps with cytokinesis.
In what phase of the cell cycle does DNA synthesis occur?
S phase (part of interphase). Between G1 and G2.
What is a true-breeding strain?
What is a monohybrid cross vs a dyhybrid cross?
Experiment where one factor is crossed with one factor, rather than two factors being crossed with two factors.
What is the F1 generation, and what does F1 generation look like?
o Offspring produced by crossing 2 true-breeding strains
o All F1 plants resembled only one parent
• Dominant character
• Alternative character recessive
o No plants with intermediate (blended) characteristics
What is the F2 generation, and what does F2 generation look like?
• F2 generation (second filial generation)
o Offspring resulting from the self-fertilization of F1 plants
o Recessive trait reappeared among some F2 individuals
o Phenotypic ratio 3:1 (3 purple flowers to one white flower)
o Genotypic ratio 1:2:1
• 1 true-breeding dominant plant (TT)
• 2 not-true-breeding dominant plants (Tt, Tt)
• 1 true-breeding recessive plant (tt)
What is Mendel's Law of Segregation?
Alleles separate themselves during meiosis and end up in different gametes.
What is an example of incomplete dominance?
Snap dragon flower color - colors blend to make pinks instead of distinct red or white
What is an example of codominance?
AB Blood type (You can be A, B, or A+B)
What is an example of having multiple alleles to code for the same thing?
A, B, O blood type (more than 2 alleles)
What is pleiotropy? What is an example of pleiotropy?
Pleiotropy is when one allele has multiple phenotypic effects, e.g. influences more than one thing
Pleio- = more
-trophy = growth or development (e.g. atrophy)
Ex: Sickle cell anemia (same gene also codes for malaria protection) or cystic fibrosis
What is an example of epistasis?
Coat color in labrador retrievers
What does the term polygenic inheritance mean? What is an example?
You inherit genes from more than one source (2 parents)
Poly- = many
-genic = genes
Example: height, skin color, eye color...not just 2 combinations
How do you write a trait with incomplete dominance?
Capital or lower-case letter + superscript letter or number
What is epistasis? Example?
One gene acts as the "modifier" for another set of genes, e.g. in Labrador retrievers, where there is a gene for color (black or brown) but also a gene for color or no color (black/brown or yellow)
What are some environmental influences on genetics?
Temperature (Siamese cats' noses and ears get pigmented when cold)
What do albinism, cystic fibrosis, sickle cell anemia, and Tay Sachs have in common?
Autosomal recessive conditions
What do Achondroplasia, Huntington’s disease, Familial hypercholesterolemia, and Marfan Syndrome have in common?
Autosomal dominant conditions
Allosome vs autosome
somatic cell vs gamete? (check this)
What is X inactivation, and what are the three steps?
1) One of two X chromosomes is deactivated
2) The deactivated X chromosome condenses to form a Barr body
3) The Barr body cell is copied and spread throughout the body
Who does X inactivation affect?
All somatic cells of female mammals
What is the fancy name for alterations of chromosomes?
Aneu- = without
-ploidy = # of chromosomes
What is nondisjunction?
Failure of sister chromatids or homologues to separate properly during meiosis
What is an example of a chromosome deletion?
Cri du Chat (French for "cat's cry")
What is an example of a chromosomal duplication?
Fragile X syndrome
What is an example of a chromosomal inversion?
Chromosome breaks and reattaches upside-down
What is an example of a chromosomal translocation?
Pieces of different chromosomes are switched and sewn together, e.g. Philadelphia chromosome or thyroid cancer
What is nondisjunction of sex chromosomes?
When sex chromosomes don't align with traditional XY
What is it called when a person has XXX chromosomes?
What is it called when a person has XXY chromosomes?
What is it called when a person has X0 chromosomes?
Don't develop secondary sex characteristics
What is it called when a person has XYY chromosomes?
What is it called when a person has 0Y chromosomes?
We need an X chromosome to survive
If there is a special partial deletion on chromosome 15, it can result in Prader-Willi or Angelman syndromes. Which is which?
Prader-Willi = mild
Angelman = severe
What is the difference between diploid and haploid chromosomes?
Diploid: chromosomes in pairs - 2n
Haploid - single chromosomes - n
Are somatic cells diploid or haploid? Gametes?
Somatic cells are diploid. Gametes are haploid.
What is the longest phase of the cell's life cycle?
What is the overall genetic point of gametes having half the number of chromosomes that somatic cells do?
Increases genetic diversity through sexual reproduction.
Gametes have ½ the number of chromosomes so that they can combine with another individual’s to produce offspring that are genetically diverse (not clones)
What are the two phases of meiosis?
Meiosis 1 and Meiosis 2
What happens in the Meiosis 1 prophase?
Synapsis (homologous chromosomes interact)
Crossing over of genes
What happens in Meiosis 1 metaphase?
Chromosomes align in pairs (one on each side of the equator)
Chromosomes orient themselves randomly ("Random Alignment" aka "Independent Assortment")
What happens in Meiosis 1 anaphase?
Sister chromatids DON'T separate
What happens in Meiosis 1 telophase?
It's the same as in mitosis:
Spindle apparatus falls apart
Nuclear envelope re-formed
Ends up with 2 nuclei
What happens in Meiosis 1 cytokinesis?
Same as mitosis: cytoplasm separates into 2 distinct cells.
What is the overall product of Meiosis 2?
2 haploid cells for each cell formed in Meiosis 1
Total of 4 haploid gametes from one original cell
When does meiosis 2 happen?
Immediately after M1 (no interphase)
What is the overall product of Mitosis 1 vs. Meiosis 1?
Mitosis produces 2 diploid cells
Meiosis 1 produces 2 haploid cell
What are some sources of genetic variation in sexual reproduction?
What is Mendel's Law of Segregation?
Alleles (versions of genes) separate in gamete formation
He was describing Anaphase 1, but didn't know it at the time
When tracing pedigree, what do the circles, squares, diamonds, and shaded/white shapes mean?
Shaded - person has the disorder
Circle - female
Square - male
Diamond - sex unknown
The 9:3:3:1 genotypic ratio of an F2 dihybrid cross demonstrates what law?
Law of Independent Assortment
What is the Law of Independent Assortment?
Each allele combination is equally likely to occur
Do cleavage furrows form in plant cells, animal cells, or both?
Cleavage furrows - animal cells
Does cell plate formation occur in plant cells, animal cells, or both?
Cell plate formation - plants
What is aneuploidy?
Different number of chromosomes
Aneu- = without
-ploid = # of sets of chromosomes
How is hemophilia passed?
Sex-linked (passed on X chromosome)