lecture 8

Question 1

genetic variation

Answer 1

differences among individuals that are encoded in their DNA

• DNA and genes
• transcription and translation
• genetic code
• proteins
• mutations

Question 2

DNA: deoxyribonucleic acid

Answer 2

• DNA molecules run in an antiparallel, double helix configuration
• the hydrophilic sugar-phosphate backbone faces the exterior, nitrogenous base pairs face the interior
• four kinds of bases: adenine, thymine, cytosine, guanine (A, T, C, G)
• Purines (A, G) always pair with pyrimidines (C, T)
• A-T have two hydrogen bonds, C-G have three
• strands are complimentary
• DNA has two different sized grooves: the major groove and the minor groove

Question 3

Different sections of a gene are either:

Answer 3

a) structural - code for RNA or protein

b) regulatory - responsible for expression of genes

Question 4

Genotype to phenotype

Answer 4

a) genetic information flows from DNA to RNA to proteins
b) differences in genotype may cause difference sin phenotype; physical traits that are a product of the proteins produced

Question 5

What happens to the genotype and phenotype if there is a change in the sequence of bases in the coding region of a gene?

Answer 5

Genotype changes, because now there is a new allele. Phenotype may change, if the new allele changes the gene product.

Question 6

What happens to the genotype and phenotype if there is a change in the sequence of bases in the regulatory regions of a gene??

Answer 6

Same. Not all changes in genotype change the phenotype.

Question 7

At the molecular level, what is the “gene for flower color”?

Answer 7

A sequence (part of a chromosome) that codes for a product involved in making the pigments found in flower petals.

Question 8

At the molecular level, what is an allele?

Answer 8

Any version of a gene that differs in DNA sequence.

Question 9

Red blood cells, goblet cells, and rod cells contain the same chromosomes. Why are the cells so different?

Answer 9

they express different genes.

Question 10

When chromosomes replicate…

Answer 10

DNA is copied by enzymes. They enzymes make mistakes, at random.

Question 11

Mutations can change the fitness of an organism

Answer 11

• increase the fitness = beneficial
• no affect on the fitness = neutral
• decrease the fitness = deleterious

Question 12

unequal crossing over in chromosomes

Answer 12

is a type of gene duplication or deletion event that deletes a sequence in one strand and replaces it with a duplication from its sister chromatid in mitosis or from its homologous chromosome during meiosis.

Question 13

retroposition in chromosomes

Answer 13

In genetics, the integration of a sequence derived from RNA into a DNA genome. Messenger RNA (mRNA) is reverse-transcribed and reintegrated into the genome.

Question 14

environmental variation

Answer 14

differences among individuals due to exposure to different environments; can influence phenotype by altering gene expression

Question 15

Does environmental variation provide raw material for evolution?

Answer 15

• Environmentally induced changes in phenotype are not transmitted to future generations.
• The variation is not heritable

Question 16

What about epigenetic modification? DNA methylation?

Answer 16

• temporary inheritance, not permanent

Question 17

genotype-by-environment interactions

Answer 17

• differences among individuals in the way the environment influences phenotype that has a genetic basis.
• ex: temperature dependent sex determination (TSD)

Question 18

reaction norm

Answer 18

the pattern of phenotypes an individual may develop upon exposure to different environments

Question 19

phenotypic plasticity

Answer 19

• expression of different phenotypes by the same genotype, often in response to the environment
• may be adaptive, non-adaptive, or maladaptive