The Deal with Alleles
What is the difference between a gene and a chromosome?
A gene is DNA that codes for 1 particular trait/protein. A chromosome is a particular set of genes that are all on one molecule of DNA.
This is the important molecule at the end of the electron transport chain that is powered by hydrogen ions to make energy.
ATP synthase!
Two grandpas love fishing in a lake. They only keep the largest fish, throwing the small ones back. Over the many years they fish in the lake, the fish seem to get smaller and smaller.
What kind of selection is this?
Natural selection (we don't WANT them to be smaller!)
A cell has a haploid number of 51. What is its diploid number?
2n = 102!
This is the exact other input for cellular respiration that is NOT glucose.
6O2.
What is an example of two alleles for the same gene?
Brown hair and red hair color
More pheomelanin/more eumelanin (MC1R gene)
Light or dark coat color in pocket mice
Brown eyes/blue eyes
Etc
We can use these molecules on DNA prior to gel electrophoresis to eventually see how long particular parts of the DNA are.
What is one phenomenon that could lead to traits that are NOT adaptive in a population?
Anything genetic drift (bottleneck, founder effect, randomness)
How many sister chromatids are present in a human cell at the very beginning of meiosis?
92 (2 x 46, as we have copied every homologous pair).
R group/sidechain
Two flowering plants are crossed that follow Mendelian inheritance. Red petals are dominant to pink petals. Both flowers are heterozygotes. Complete a Punnett square and predict the phenotypic ratios of the offspring.
3:1 red:pink
What is the purpose of histones, and how SPECIFICALLY do they interact with DNA?
They bond ionically with DNA (histones positive, DNA negative) to wrap DNA up like a spool, packaging it tightly in the nucleus.
Give one example of sexual selection. Why does this NOT help with survival?
~Many choices~ but sexual selection helps with mate choice/reproduction and can detriment survival!
A cell has a diploid number of 6. Draw an image of the genetic material in the cells that would produced at the end of meiosis (during telophase 2).
3 single chromatids!
This is what we added to wells to test the blood types during the crime lab.
Anti-A and Anti-B antibodies.
A woman who is a carrier for red-green colorblindness marries a man who is red-green color blind. Is it possible that none of their children are color blind?
Yes. Daughter could be carrier and son could get non-carrying allele from mom.
How are nucleotides held together between the two strands of DNA, and how does this connection work on a molecular level?
The lodgepole pine has cones that only open and release seeds after the heat of a wildfire. Why might this be an adaptation for the pine?
Less competition of other plants! Seeds have plenty of room and light.
True or false: DNA must be replicated in preparation for mitosis once, and for meiosis twice.
FALSE! Replicated once for both processes, in interphase.
Give an example of a disease caused by a substitution mutation.
Sickle cell anemia or achondroplasia
Why don't blood types follow Mendelian inheritance? Draw an image to support your answer of a red blood cell.
Blood cells can be codominant for antigens, meaning that they can have both B antigens and A antigens at the same time (or the recessive allele, O, which codes for no antigens)
A recently-made strand of mRNA is 20% uracil. What percentage of its template strand of DNA is adenine?
20%. If we were looking at a whole molecule of DNA, we could also figure out the percentage of cytosine and guanine!
Dragons in the Kingdom of Nabru come in different shades, ranging from pink to blue. The sky is blue and the ground is pink in Nabru. Over time, purple dragons slowly become rarer and rarer. Explain why there are less purple dragons and what type of selection this is.
There are less purple dragons because selective pressures have led to better survival of the camouflaged blue and pink types. This is an example of disruptive selection.
What are three differences between mitosis and meiosis?
1. Meiosis involves 2 divisions (mitosis 1)
2. Meiosis creates haploid cells (mitosis diploid/exact copies)
3. Meiosis happens in gametes, mitosis in somatic cells. (or for sexual reproduction vs. for repair and growth)
Why are flowering plants so much more successful than other types of plants?
Sexual reproduction leads to a lot of genetic diversity, allowing them to spread and survive in lots of environments!