Essential Concepts

Question 1

microevolution

Answer 1

the changes in the frequency of speci c variants of genes in a population over the course of several generations.

Question 2

chromosomes

Answer 2

23 unique strands of DNA that contain many genes. We have two copies of each—one from our mother and one from our father, for a total of 46.

Question 3

alleles, and their two types

Answer 3

The two copies of chromosomes inherited from parents. They can either be the same (homozygous) or different (heterozygous).

Question 4

The three mechanisms by which allele frequency in a population can change.

Answer 4

natural selection

genetic drift, which is caused by random sampling, or the effect of chance;

gene flow, or the transfer of alleles between populations.

Question 5

Hardy-Weinberg law

Answer 5

determines the allele frequency in a population that is not evolving. That is, allele frequency should remain constant from generation to generation when the population is not affected by natural selection or other causes of allele frequency shifts, such as genetic drift and gene flow.

Question 6

5 characteristics, according to Hardy Weinberg Law of a population who’s genes are NOT changing

Answer 6

1. There can be no mutations.
2. The population should engage in random mating.
3. There cannot be natural selection.
4. The population should be very large.
5. There can be no gene flow.

Question 7

Mendel’s Two Laws of Inheritance

Answer 7

The law of segregation: for every characteristic, such as eye color or hair color, each parent possesses two possible versions of that characteristic and that during the reproductive process, these two traits, known as alleles, are separated (that is, segregated), with only one version passing on to the offspring.

The law of independent assortment: alleles of multiple traits segregate and are shuffled independently of one another. If you have two traits that get passed down, the alleles in each offspring are independent—that is, having one allele of trait A doesn’t have any effect on which allele of trait B the offspring is likely to inherit.

Question 8

Gene

Answer 8

A distinct chain of DNA—deoxyribose nucleic acid—that contains the biochemical instructions for the production of a protein.

Question 9

Introns

Answer 9

“Junk DNA” that is coiled tightly with genes into little bundles called chromosomes. Junk DNA doesn’t provide any code for proteins, the usual function of DNA, but it likely has some other biological function related to genetics. We just don’t know what that is yet.

Question 10

Four bases of DNA

Answer 10

adenine (A), guanine (G), cytosine (C), and thymine (T), each made up of different combinations of nitrogen, carbon, oxygen, and hydrogen. Their different combinations of elements give them different shapes.

Question 11

The two steps that convert DNA into proteins

Answer 11

transcription and translation

In essence, transcription and translation involve copying the information in DNA, putting it into a portable form, and transporting it out of the nucleus to other parts of the cell, where the cell’s manufacturing machinery can construct the new protein.

Question 12

RNA

Answer 12

ribonucleic acid (RNA), a for Of messenger molecule that communicates the genetic code of DNA.

Question 13

One major difference between the chemical makeup of DNA and RNA

Answer 13

RNA uses uracil (U) instead of thymine as the binding partner for adenine.

Question 14

RNA polymerase

Answer 14

binds to the DNA and acts to separate the DNA’s bound base pairs, effectively unzipping the double helix. As it does so, moving across the DNA strands like the slider body of a zipper, the RNA polymerase reads the DNA sequence and creates a complementary, matching sequence of RNA.

Question 15

Codons

Answer 15

triplets of nucleotides corresponding to specific amino acids.

61 of them code for amino acids. There are three additional ones that code for the instructions “start” and “stop,” similar to a telegram.

Question 16

Ribosome

Answer 16

An enzyme complex that binds to the RNA and moves across the sequence, reading the codons in turn and catalyzing reactions that sequester and add amino acids into an elongated chain. The creation of the elongated chain ends when the ribosome encounters a “stop” codon.

Question 17

Gene Expression

Answer 17

The general process of translating and transcribing a gene.

Question 18

Histone acetylation

Answer 18

Process that relaxes or loosens the DNA structure around the nucleosomes (a combination of histones and DNA).

Question 19

Decondensation

Answer 19

The process that facilitates the transcription of genes by enzymes called RNA polymerases, which are responsible for the DNA transcription process.

Question 20

Histone Deacetylases (HDACs)

Answer 20

Natural foils to the HATs which remove the acetyl groups and, in doing so, promote the return of the gene to a silent state.

Question 21

DNA methylation

Answer 21

the process of linking molecules called methyl groups to DNA nucleotides. Enzymes called DNA methyltransferases (DNMTs) help this task.

Question 22

Epigenetic changes

Answer 22

reversible modifications of DNA that do

not change the underlying genetic sequence

Question 23

Mutations

Answer 23

Permanent changes to genetic sequences that occur when a mistake is made during cell reproduction.

Question 24

Two processes cells can use to combat mistakes during cell replication

Answer 24

1. Senescence - the cell stops dividing after DNA modifications become too severe.
2. Apoptosis - the cell commits suicide.

Question 25

Oncogenes

Answer 25

Cancer-inducing genes

Question 26

Photoreceptors

Answer 26

Special cells in the retina that convert images in to electrical impulses that the brain can understand.