HCR 240 Week 1: Genes and Genetics

Flashcards for reviewing key vocabulary and concepts related to genes and genetics from HCR 240 Week 1 lecture notes.

Deoxyribonucleic Acid (DNA)

The hereditary material in cells with a double helix structure containing 4 nitrogenous bases: Adenine, Cytosine, Guanine, and Thymine.

Nucleotide

Phosphate group + pentose sugar + nitrogenous base

Complementary Base Pairing (DNA)

A bonds with T, C bonds with G

Complementary Base Pairing (RNA)

A bonds with U, C bonds with G

Codon

Triplets of nucleotides (3) that code for a specific amino acid.

Stop Codons

3 out of 64 possible codon combinations that signal the end of protein synthesis.

DNA Replication

Process where the DNA strand is untwisted and unzipped, single DNA strands act as a template, and DNA polymerase adds new nucleotides and proofreads.

Base pair substitution (point mutation)

One base pair is incorrectly substituted for another.

Silent mutation

Incorrect base pair still codes for correct amino acid

Nonsense mutation

Incorrect base pair codes for stop or nonsense codons

Missense mutation

Incorrect base pair codes for incorrect amino acid

Mutagens

ROS, radiation, toxic chemicals that can cause errors during the proofing process or changes to the parent DNA, leading to mutations.

Frame shift mutations

Insertion or deletion of one or more base pairs, altering all subsequent codons and often leads to premature stop codons.

Transcription

RNA is synthesized from a DNA template via RNA polymerase.

RNA Splicing

Process where mRNA is removed from the nucleus, matures through the removal of introns, and extrons are combined to form functional mRNA.

Translation

Functional mRNA is converted into polypeptides with the assistance of ribosomes and transfer RNA (tRNA).

Somatic cells

Contain 46 chromosomes (23 pairs); diploid cells.

Gametes

Sperm and egg cells; contain 23 chromosomes; haploid cells.

Meiosis

Formation of haploid cells from diploid cells

Autosomal Chromosomes

22 out of 23 chromosome pairs that are not sex-related.

Sex Chromosomes

The 23rd pair of chromosomes that determine the genotypical sex of the child; XX: female, XY: male.

Polyploidy

Cells with 3 or more copies of each chromosome; fetuses do not survive.

Aneuploidy

Cells with an abnormal number of one particular chromosome, typically a result of nondisjunction.

Down syndrome

Trisomy 21; increased risk of congenital heart defects, respiratory infections, leukemia, and Alzheimer disease.

Turner Syndrome

Females have only one X chromosome (45,X); absence of ovaries (sterile), short stature, webbing of the neck.

Trisomy X

Females have three or more X chromosomes; symptoms are variable and include sterility, menstrual irregularity, and/or cognitive deficits.

Klinefelter syndrome

Males have at least one Y and two or more X chromosomes; characteristics include: overall male appearance, gynecomastia, small testes, sparse body hair.

Fragile X Syndrome

Site is on the long arm of the X chromosome; has an elevated number of repeated DNA sequences (CGG); intellectual disabilities, behavioral problems, long and narrow faces.

Allele

Different forms of a gene; typically inherit one from mother and one from father.

Homozygous

Alleles that are identical (AA or aa).

Heterozygous

Alleles that are different (Aa).

Dominant Allele

Allele with observable effect (denoted by capital letter).

Recessive Allele

Allele with non-observable effect in the presence of a dominant allele (denoted by lowercase letter).

Co-Dominant Allele

Both alleles have an observable affect (example: blood type AB).

Genotype

Composition of genes at a given locus.

Phenotype

Outward appearance of an individual (genotype + environment).

Carrier

Individual with disease-causing allele but with a normal phenotype; most typically occurs with heterozygous alleles.

SRY

Sex-determining region on the Y chromosome.

Autosomal Dominance

Condition is expressed equally in males and females (not sex-linked).

Germline mosaicism

Parent carries the mutation in his or her gamete cells but does not have the autosomal dominant disease in his or her somatic cells (parent with normal phenotype; asymptomatic carrier).

Penetrance

Percentage of individuals who have the diseased genotype and express the diseased phenotype.

Incomplete penetrance

90% of people with the gene mutation for retinoblastoma (eye tumor) will have the disease and 10% will not.

Age-dependent penetrance

People with the genes for Huntington’s disease will not show symptoms until they are in their 30-40s.

Expressivity

Extent of variation in a phenotype associated with a particular genotype.

Autosomal Recessive

Person must be homozygous to express the disease (dd) meaning both parents must be carriers (dd or Dd).

Cystic fibrosis

Mutated gene forms defective chloride channels, which leads to a salt imbalance that results in abnormally thick, dehydrated mucus.

Consanguinity

Mating of two related individuals (also known as inbreeding).

X-Linked Dominant

Females are more likely to be affected than males; males who have it have a 100% chance of passing it to their daughters and a 0% chance of passing it to their sons.

X-Linked Recessive

Males are significantly more likely to be affected; an affected father will never be able to pass the gene to his sons and will always pass the gene to his daughters, who will then become carriers.

Duchenne Muscular Dystrophy

Deletion of DMD gene causes dystrophin to not work properly; consequently, muscle cells do not survive.

Barr body

The deactivated chromosome in females to correct for having two X chromosomes.