Genetic Variation: Its Origin and Detection

Flashcards covering genetic variation, mutation types, human hemoglobin disorders, research techniques like PCR and Southern blotting, and population genetic principles.

Mutations in __________ cells can be transmitted from one generation to the next, while those in somatic cells cannot.

germline

A gene’s location on a chromosome is termed a __________.

locus

In human genetics, DNA sequence variants that are more common in populations, typically with a frequency greater than $1\%$, are described as __________.

polymorphisms

The term __________ comes from a Latin root meaning "to hide," describing alleles whose effects are not physically observable in a heterozygote.

recessive

Base-pair substitutions that do not change the amino acid sequence due to the redundancy of the genetic code are called __________ __________.

silent substitutions

__________ mutations produce one of the three stop codons ($UAA$, $UAG$, or $UGA$) in the mRNA, resulting in premature termination of a polypeptide.

Nonsense

A __________ mutation occurs when the number of missing or extra base pairs is not a multiple of three, altering all codons downstream from the site.

frameshift

In Charcot–Marie–Tooth disease type 1A, an increased dosage of the __________ gene product due to a duplication on chromosome $17$ contributes to demyelination.

PMP22

Splice-site mutations can occur at the $GT$ sequence that defines the $5'$ donor site or the __________ sequence that defines the $3'$ acceptor site.

AG

The autosomal dominant disorder known as familial hypercholesterolemia is an example of __________, where $50\%$ of the gene product is insufficient for normal function.

haploinsufficiency

Sickle cell disease is typically caused by a single missense mutation that substitutes __________ for glutamic acid at position $6$ of the $\beta$-globin chain.

valine

In $\beta$-thalassemia, an excess of $\alpha$ chains forms __________ that damage the cell membranes of red blood cell precursors.

homotetramers

Ultraviolet ($UV$) radiation causes the formation of covalent bonds between adjacent cytosine or thymine bases, creating __________ __________.

pyrimidine dimers

Xeroderma pigmentosum ($XP$) is an autosomal recessive disease caused by a defect in the __________ __________ __________ ($NER$) system.

nucleotide excision repair

A mutation hot spot in humans is the dinucleotide sequence __________, where a methylated cytosine can easily lose an amino group to become thymine.

CG

The risk of producing a child with single-gene disorders like Marfan syndrome and achondroplasia is strongly correlated with advanced __________ age.

paternal

In the MN blood group system, the heterozygote can be distinguished from both homozygotes, meaning the alleles are __________.

codominant

__________ __________ use restriction endonucleases to cleave DNA at specific sites and labeled probes to visualize specific fragments.

Southern blots

Short tandem repeats ($STRs$) are polymorphisms involving repeats units that are typically __________ to __________ bp long.

$2$; $5$

The polymerase chain reaction ($PCR$) process involves three basic steps: DNA denaturing, __________ __________, and primer extension.

primer hybridization

The dideoxy method of DNA sequencing, invented by Frederick Sanger, uses chain-terminating __________ to identify the position of specific bases.

dideoxynucleotides

The __________ __________ states that if two trials are independent, the probability of obtaining a given outcome in both is the product of the individual probabilities.

multiplication rule

In the Hardy–Weinberg equation ($p^2 + 2pq + q^2 = 1$), the term __________ represents the frequency of heterozygotes in the population.

$$2pq$$

__________ __________ is a random evolutionary process that produced larger changes in gene frequencies in smaller populations, such as in the Old Order Amish.

Genetic drift

The predictable relationship between the introduction of harmful alleles by mutation and their removal by natural selection is called __________-__________ __________.

mutation-selection balance