Unit 4 Exam Review: Genetic Inheritance and Human Reproduction

A complete set of vocabulary flashcards covering genetic inheritance concepts, non-Mendelian genetics, chromosomal abnormalities, human reproductive structures, and embryonic development stages based on the Unit 4 Exam Review study guide.

Gregor Mendel

The father of genetics who researched pea plants.

Law of Segregation

A genetic principle stating that $2$ alleles for each gene are placed in different gametes during meiosis.

Law of Independent Assortment

A genetic principle stating that the allele a gamete receives for one gene is not influenced by the allele it receives for another gene.

Epistasis

A genetic interaction where one gene masks or modifies another gene, such as coat color in Labrador retrievers.

Pleiotropy

A genetic condition where one gene affects multiple traits.

Polygenic Inheritance

A pattern of inheritance where many genes contribute to one trait.

Alleles

Alternate forms of a gene.

Genotype

The genetic makeup of an organism.

Phenotype

The physical appearance of an organism.

Dominant Allele

An allele that occurs more often in a population, masks the recessive allele when both are present, and is represented by an uppercase letter.

Recessive Allele

An allele that occurs less often in a population, is masked by the dominant allele when both are present, and is represented by a lowercase letter.

Homozygous

Having two identical alleles for a gene, such as dominant homozygous ($AA$) or recessive homozygous ($aa$).

Heterozygous

Having two different alleles for a gene, represented as $Aa$.

Incomplete Dominance

A mix or blend expression of traits in heterozygous genotypes, such as red ($RR$) and white ($rr$) snapdragon flowers producing pink ($Rr$) flowers.

Codominance

An expression of both traits equally, such as the $AB$ blood type or patchwork fish ($Bb$).

Sex Chromosomes

The $23\text{rd}$ pair of chromosomes that determine biological sex or gender ($XX$ in females and $XY$ in males).

Sex-Linked Traits

Traits carried on sex chromosomes, most commonly carried on the $X$ chromosome and most likely to affect males.

Pedigree

A chart showing inheritance through generations.

Gamete

A haploid sex cell, specifically a sperm or an egg, produced by meiosis.

Zygote

A fertilized egg formed by the fusion of sperm and egg.

Embryo

An early developing human up to $8\,\text{weeks}$ of development.

Fetus

A developing human from $9\,\text{weeks}$ to birth, named such at $2\,\text{months}$.

Spermatogenesis

The production of sperm, which occurs in the testes.

Oogenesis

The production of eggs, which occurs in the ovaries.

Ovulation

The release of an egg (ovum) from the ovary.

Fertilization

The fusion or joining of sperm and egg that occurs in the fallopian tube (oviduct).

Implantation

The attachment of the blastocyst to the wall of the uterus.

Mitosis

The cellular process responsible for growth and cell division following fertilization.

Nondisjunction

The failure of chromosomes to separate properly during meiosis.

Down Syndrome

A condition that occurs when an offspring inherits $3$ copies of chromosome $21$.

Edwards Syndrome

A condition that occurs when an offspring inherits $3$ copies of chromosome $18$.

Turner Syndrome

A condition that occurs when a female inherits only $1$ copy of the $X$ chromosome.

Ovary

Female reproductive organ that produces eggs and the hormones estrogen and progesterone.

Fallopian Tube

The site of fertilization that transports the egg to the uterus (also known as the oviduct).

Uterus

The reproductive organ that serves as the site of blastocyst implantation and fetal development.

Amniotic Sac

The fluid-filled sac that protects the developing embryo in the uterus.

Vagina

The birth canal that receives sperm during reproduction.

Testes

Male reproductive organs that produce sperm and the hormone testosterone.

Epididymis

The male reproductive structure that stores and matures sperm.

Vas Deferens

The duct that transports sperm.

Urethra

A duct in males that carries semen and urine at different times.

Cleavage

Rapid mitosis of the zygote following fertilization.

Blastula

An early developmental structure consisting of a hollow ball of hundreds of cells.

Gastrulation

The developmental process that forms the three primary germ layers.

Ectoderm

The embryonic germ layer that forms the nervous system and skin.

Mesoderm

The embryonic germ layer that forms muscle, bone, and the circulatory and reproductive systems.

Endoderm

The embryonic germ layer that forms the lining of the digestive system and respiratory tract.

Organogenesis

The phase of embryonic development where organs form, during which the brain and spinal cord of the nervous system develop first.

First Trimester

Weeks $1-12$ of development, most affected by exposure to chemicals or radiation because organ systems are forming and cells are rapidly dividing.

Second Trimester

Weeks $13-24$ of development, during which the baby begins to move, a fetal heartbeat can be detected, and biological sex can be determined.

Third Trimester

Weeks $25-40$ of fetal development.