Week 5 Notes: The Inheritance of Traits — Vocabulary

Vocabulary flashcards covering key genetic concepts, terms, and disorders from Week 5 notes on the inheritance of traits.

Newborn screening

Mandatory U.S. testing of about 4 million newborns annually, performed roughly 24 hours after birth using a heel-prick blood sample to screen for 47 disorders; a positive result indicates disease, but many results are false positives.

Heel-prick blood sample

The small blood sample taken from a newborns heel for screening tests.

Positive result (newborn screening)

Indicates that a disease-related abnormality was detected in the screening test.

False positive (newborn screening)

A test result suggesting disease when no disease is actually present; common in newborn screenings.

Zygote

A single-celled fertilized egg formed when sperm and egg fuse.

Embryo

Stage after the zygote that develops into a fetus.

Fetus

Developing human from about eight weeks of gestation to birth.

Gamete

A reproductive cell (sperm or egg) that is haploid and participates in fertilization.

Diploid

Two complete sets of chromosomes (humans have 46 in body cells).

Haploid

One complete set of chromosomes (gametes are haploid).

Allele

A different version of the same gene.

Mutation

An error in copying DNA; can be neutral, beneficial, or dysfunctional.

Neutral mutation

A mutation that has no beneficial or harmful effect on the organism.

Beneficial mutation

A mutation that increases an organism's fitness.

Dysfunctional mutation

A mutation that impairs function or causes disease.

Meiosis

Cell division that produces haploid gametes and increases genetic diversity.

Segregation

Allele pairs separate into different gametes during meiosis.

Independent assortment

Homologous chromosomes separate randomly during meiosis I, increasing genetic variety.

Punnett square

A chart used to predict offspring genotypes from parental genotypes.

Phenotype

An individual's observable physical traits.

Genotype

The genetic makeup of an individual; the combination of alleles.

Homozygous

Two identical alleles for a gene.

Heterozygous

Two different alleles for a gene.

Dominant

An allele or trait that is expressed in either homozygous or heterozygous form.

Recessive

An allele or trait that is expressed only when homozygous.

Mendel

Gregor Mendel, often called the father of genetics for his rules of inheritance from pea plants.

Pedigree

A family tree used to study inheritance patterns across generations.

Incomplete dominance

A situation where heterozygotes show a blended phenotype.

Codominance

Both alleles are fully expressed in heterozygotes.

Krabbe disease

A recessive disorder caused by GALC mutations; leads to myelin loss and progressive decline, often fatal by age 3; not always included in newborn screening.

Galactosemia

Inability to digest galactose causing buildup of sugar in multiple organs.

Cystic fibrosis

Most common recessive disease in Europeans; defect in chloride transport leading to thick mucus; average lifespan about 40 years.

Sickle cell disease

Inherited disorder from two mutant hemoglobin alleles; painful crises and organ damage; carriers have some normal hemoglobin.

SRY gene

Sex-determining region on the Y chromosome that triggers male development.

Sex chromosomes

Chromosome pair that determines sex; humans have 23rd pair: XX female, XY male.

X-linked traits

Traits carried on the X chromosome; often more severe in males.

Carrier

A heterozygous individual for a recessive allele who usually shows no disease but can pass the allele to offspring.

Autosomal dominant

Trait that appears in every generation; affected individuals often have an affected parent.

Autosomal recessive

Trait that can skip generations; carriers can have affected children if both parents carry the allele.

ABO blood group

System with IA, IB, and i alleles that determine red blood cell surface sugars and blood type.

I^A

Allele for A antigen contributing to Type A blood.

I^B

Allele for B antigen contributing to Type B blood.

i

O allele; no A or B antigens, contributing to Type O when homozygous.

Blood transfusion compatibility

Blood groups must be compatible to avoid immune reactions during transfusion.

Universal donor

Type O blood; can donate to any recipient.

Universal recipient

Type AB blood; can receive from any blood type.

STRs (short tandem repeats)

Short repeated DNA sequences used in DNA profiling to distinguish individuals.

DNA profiling

Technique to identify individuals based on DNA sequence differences; formerly called DNA fingerprinting.

PCR (polymerase chain reaction)

Technique that amplifies DNA by cycling through heating and cooling.

Taq polymerase

Heat-tolerant enzyme used in PCR to synthesize DNA.

Gel electrophoresis

Method to separate DNA fragments by size using an electric field.

Random fertilization

Any sperm can fertilize any egg, producing many possible offspring combinations.

64 trillion combinations

The estimated number of possible offspring from 8 million x 8 million random fertilizations.

13 STR regions

The standard number of STR regions used for DNA profiling in many analyses.

Environmental sex determination

Sex determination influenced by environmental factors in some non-human organisms.

ZW/ZZ

Bird sex determination system: females are ZW and males are ZZ.

Bees and ants

In some species, fertilized eggs become females and unfertilized eggs become males.