BICD 100 practice

genotype

genetic makeup of an organism

phenotype

an observable, measurable trait (physical appearance too)

-ex) ex) IQ, smell, protein amount

After eating asparagus, some people can smell asparagus odor in their urine?

Yes, It is an observable trait. There is genetic

Is a person's I.Q. a phenotype?

Yes, IQ is a measurable trait. It is influenced by both genetic and environmental factors

An increase in protein abundance. For example, allele 1 of a particular gene results in 10× more protein being produced than allele 2. Is this a phenotype?

Yes, Protein abundance can be measured. It is the result of gene expression. It is an observable molecular characteristic of the organism.

phenotype in influenced by

physical traits, development, environment, biochemical and physiological traits, behavior

homologous chromosomes

a pair of chromosomes that are the same size, and have the same genes in the same location (loci)

before replication each DNA molecule had

1 chromatid

after replication each DNA molecule has

2 chromatids (pulled apart in mitosis)

promoter region

region of DNA that RNA polymerase attaches to to begin transcription.

enhancer

binds activator proteins that helps increase transcription

5' UTR

transcribed but not translated, helps the 40S subunit of the ribosome bind

• CONTAINS THE REGULATORY SEQUENCE

Exons

expressed sequence of DNA; codes for a protein

introns

sequence of DNA that is not involved in coding for a protein and is cut out by spliceosome, used for structural support

3' UTR

comes before the polyadenylation signal transcription to stop (AATAAA)

central dogma

DNA --> RNA --> protein

regulatory regions

promoter and enhancer/silencer

silencer binds

repressor proteins which decrease transcription

coding sequence on DNA

the parent strand, mRNA is complementary to it

alternative splicing

spliceosome can decide which exons to splice in and out, resulting in different mRNA and protein

gene

DNA seq used transcribed to produce functional proteins

locus

location within the genome (may or may not contain gene)

southern blot

detects DNA sequence

northern blot

detects RNA sequence

gel electrophoresis: smaller fragments move

further down

ladder

used to estimate length of unknown DNA/RNA fragments

size of band

number of nucleotides

thickness of band

how many copies

• more copies = thicker band

heterozygote on gel

one band with slightly thinner thickness on dominant allele and another similar band on the recessive allele

mutation

change in DNA seq

silent mutation

DNA sequence changes but amino acid is not affected

missense mutation

one amino acid is changed

nonsense mutation

early stop codon is reached

frameshift mutation

if NOT A multiple of 3, an insertion/deletion can shift the remaining amino acids down the road

start codon and function

AUG; est. reading frame

stop codons

UAA, UAG, UGA

whatever affects mRNA affects the…

protein

loss of function mutation

makes less functional protein, reduces/eliminates the normal genetic function of the product (often recessive)

gain of function mutation

a mutation that confers new or enhanced activity on a protein (often dominant)

• can lead to over-regulation of genes

duplication

repeated DNA segment

Translocation

chromosome segments move/swap locations

allele

alt version of the same gene

diploid

(genetics) an organism or cell having two sets of chromosomes or twice the haploid number

• carries 2 alleles at most

• one copy of he chromosome inherited from each parent

Haplosufficiency

One functional copy of a gene is enough to produce the normal phenotype. Heterozygote phenotype is normal

Haploinsufficiency

One functional copy of a gene is not enough to produce the normal phenotype.

• In a heterozygote (a⁺/a⁻), the functional allele does not provide enough gene product

• Heterozygote phenotype is altered

detect phenotype from a bar graph w/error bars

look at the heterozygote and see if it is close to any of the homozygous phenotypes. if it is, then the closest bar is dominant

incomplete dominance

A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. resulting offspring have a phenotype that is a blending of the parental traits.

codominance

A condition in which both alleles for a gene are fully expressed

if the punnett square doesn't yield the predicted phenotype we can assume

that one of the genotypes is lethal

penetrance

same mutated genotype, asking if the phenotype associated w/mutation show up in the ind?

incomplete penetrance

Not all individuals with a mutant genotype show the mutant phenotype

variable expressivity

individuals with the same genotype may have varying range phenotypes (dif severity)

epigenetics

the study of environmental influences on gene expression that occur without a DNA change

methylation

adding Met amino acids to CpG sites on DNA

more methylation on promoters

limits transcription

less methylation

increases transcription

More histone acetylation leads to

more open chromatin, transcription increases

histone DE-acetylation

closed chromatin, genes off, less transcription

Which of the following is true?

B. Methylation of a promoter sequence decreases the transcription rate for that gene

effect of certain env influences

depends on phenotype

n=

copies of each chromosome

2n/n=

number of chromosomes in a cell

In a heterozygous individual (b2/b5), what are moving away from each other in anaphase of mitosis?

Sister chromatids that have replicated copies of the same alleles

somatic mosaicism

2 genetically distinct genetic populations of cells in an individual

mosaicism occurs from…

nondisjunction

nondisjunction

unequal separation of chromosomes (1 cell has 3 and another cell has 1 chromosome)

if a cell is missing a chromosome the correct notation is

2n-1/n+1

if a cell has gained a chromosome the correct notation is

2n+1/n+1

Aneuploidy

gain or loss of one or more individual chromosomes

polyploidy

condition in which an organism has extra sets of chromosomes

law of independent assortment

inheritance of one trait is not dependent on in heritance of another trait

crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

• leads to genetic diversity

In a heterozygous cell with the genotype D/d, what separates during Anaphase I of meiosis? (assuming no crossing over has occurred)

homologous chromosomes that have different alleles

In a heterozygous cell with the genotype D/d, what separates during Anaphase II of meiosis? (assuming no crossing over has occurred)

sister chromatids that have replicated copies of the same alleles

trisomy 21

down syndrome, extra copy of chromosome 21

Approximately 2-3% of people with Down syndrome have mosaic Down syndrome. Compared with people with non-mosaic Down syndrome, would you expect their symptoms to be:

Less severe.

Which of the following best describes the genome of a cell?

All of the DNA in a cell.

In the picture below, each grey bar represents a double-stranded DNA molecule, and the black circle is the centromere. This picture represents a:

Chromosome composed of two sister chromatids. Chromosome that has undergone DNA replication.

Which of the following best describes the chromosome sets in a typical diploid human somatic cell?

Two sets of 23 chromosomes, including 22 pairs of autosomes and one pair of sex chromosomes

Alternative splicing (select one):

Is a normal process that can produce different mature mRNAs from the same pre-mRNA

Two parents are both heterozygous carriers (Aa) for the CFTR gene. The A allele produces a functional CFTR protein, while the a allele does not. What is the fundamental difference between allele A and allele a?

They have different DNA sequences.

The MLH1 gene is located on chromosome 3 in humans, and four different alleles have been identified in the population. The maximum number of different alleles of MLH1 that a single normal individual can have is:

2 alleles. Humans are diploid, meaning they have two copies of chromosome 3—one inherited from the mother and one from the father. Although four different alleles of the MLH1 gene exist in the population, one individual can only carry two alleles at that gene locus:

One allele on the maternal chromosome 3

One allele on the paternal chromosome 3

Huntington's disease is caused by a mutation in the HTT (huntingtin) gene. Individuals who inherit one mutant copy of the gene usually develop the disease, even if their second copy of the gene is normal. Based on this information, how is the disease-associated allele inherited?

autosomal dominant

Which of the cells represented below could start meiosis right away and complete the process successfully?

cell with 2 chromosomes (Each one has 2 chromatids)

If the promoter region of a gene is more methylated under environmental condition A and less methylated under condition B, in which condition will MORE mRNA be transcribed from this gene?

B

Individuals with a particular genotype were exposed to two environments: drought and non-drought. If the phenotype of growth is only controlled by genotype, and not influenced by environment, what would you expect to find?

Growth would be the same under both environmental conditions

The end result of mitosis is

two cells with the same genetic content as the parent cell.

DNA replication occurs before

mitosis and meiosis

What is the difference between a pair of sister chromatids and a pair of homologous chromosomes?

Sister chromatids are present in both mitosis and meiosis, whereas homologous chromosomes are present only during meiosis.

Sister chromatids have the same alleles of the same genes, whereas homologous chromosomes may have different alleles of the same genes.

What is an X-linked trait?

A trait determined by a gene on the X chromosome

Why can typical XX and XY individuals develop normally despite having different numbers of X chromosomes?

One active copy of most X-linked genes is sufficient for typical development.

If two parents are both carriers of an autosomal recessive genetic disease, what is the probability that they will have a child who is affected (homozygous for the recessive allele)?

1/4

In ferrets, brown color is determined by a dominant allele A, and albino color is controlled by a recessive allele a. A brown ferret is crossed to an albino ferret. This cross produces 10 brown and 11 albino offspring. What are the genotypes of the parents?

Aa and aa

If the parents were Aa and aa, half of the offspring would be Aa (brown) and half of the offspring would be aa (albino).

Which type of cross follows two characteristics simultaneously?

dihybrid