Biology Practice: Cell Division and Inheritance

These flashcards cover cell division (mitosis and meiosis), Mendelian genetics, inheritance patterns, and chromosomal alterations based on the provided learning objectives.

What are the $3$ main reasons why multicellular organisms need their cells to divide?

growth, repair, and reproduction.

In what types of cells do mitosis and meiosis each take place?

Mitosis takes place in somatic (body) cells, while meiosis takes place in germ cells to produce gametes.

Does either mitosis or meiosis change the number of chromosomes in a cell?

Mitosis results in daughter cells with the same number of chromosomes, whereas meiosis reduces the chromosome number by half.

What is the difference between a replicated (duplicated) chromosome and an unreplicated (unduplicated) chromosome?

An unreplicated chromosome consists of a single DNA molecule, while a replicated chromosome consists of two identical DNA molecules called sister chromatids.

What is the function of a centromere?

The centromere is the region where two sister chromatids are joined together.

What process must occur before any cell division takes place?

DNA replication must occur before cell division.

What is an allele?

An allele is an alternative version of a gene.

What are the definitions of a gamete, fertilization, and a zygote?

A gamete is a haploid reproductive cell (sperm or egg); fertilization is the fusion of gametes; and a zygote is the diploid cell resulting from fertilization.

What is a karyotype and how are chromosomes grouped in this procedure?

A karyotype is an ordered display of an individual's chromosomes, which are grouped into homologous pairs based on length, centromere position, and staining pattern.

How many pairs of autosomes and sex chromosomes do humans normally have?

Humans normally have $22$ pairs of autosomes and $1$ pair of sex chromosomes.

What sex chromosomes are found in genetically typical human males and females?

Males have $XY$ sex chromosomes and females have $XX$ sex chromosomes.

What are the human haploid and diploid chromosome numbers?

The haploid number ($n$) is $23$ and the diploid number ($2n$) is $46$.

What are homologous pairs of chromosomes?

Homologous pairs are two chromosomes that carry genes controlling the same inherited characteristics, with one inherited from each parent.

What is the chromosome number before and after meiosis?

The cell starts as diploid ($2n$) before meiosis and the resulting daughter cells are haploid ($n$) after meiosis.

What is the result of one cell going through meiosis?

The result is $4$ haploid daughter cells.

During which phase of meiosis does crossing over occur?

Crossing over occurs during Prophase I.

What determines how homologous pairs of chromosomes line up during metaphase I to contribute to independent assortment?

The orientation of homologous pairs is determined by random chance at the metaphase plate.

What is the blending hypothesis of inheritance, using horse coat color as an example?

The blending hypothesis suggests that parental traits mix like paint, such as a black horse and a white horse producing gray offspring.

Why did Mendel use pea plants for his inheritance experiments?

Mendel used pea plants because they have easily distinguishable characters, short generation times, and he could strictly control their mating.

What are the definitions of trait and character?

A character is a heritable feature that varies among individuals (such as flower color), and a trait is a specific variant of a character (such as purple or white flowers).

What do the terms $P$ generation, $F1$ generation, and $F2$ generation represent?

$P$ is the parental generation, $F1$ (first filial) is the offspring of the $P$ generation, and $F2$ (second filial) is the offspring of the $F1$ generation.

Distinguish between genotype and phenotype.

Genotype is the genetic makeup (the alleles an organism has), while phenotype is the organism's physical appearance or observable traits.

How are homozygous dominant, homozygous recessive, and heterozygous genotypes represented by letters?

Homozygous dominant is represented as $AA$, homozygous recessive as $aa$, and heterozygous as $Aa$.

What is Mendel’s law of segregation?

The law of segregation states that the two alleles for a heritable character separate during gamete formation and end up in different gametes.

What is the law of independent assortment?

The law of independent assortment states that each pair of alleles segregates independently of each other pair of alleles during gamete formation.

What is incomplete dominance, and what flower is used as an example?

Incomplete dominance is when the $F1$ hybrid phenotype is intermediate between the two parental phenotypes; snapdragons are a primary example.

What is codominance, and what human characteristic exemplifies it?

Codominance occurs when both alleles for a gene are fully expressed in the phenotype; human $AB$ blood type is an example.

What does the term carrier mean in genetics?

A carrier is a heterozygous individual who is phenotypically normal but carries a recessive allele for a disorder.

What is nondisjunction and what does it result in?

Nondisjunction is the failure of chromosomes to separate properly during meiosis, resulting in gametes with an abnormal number of chromosomes.

What are deletion, duplication, inversion, and translocation in chromosome structure?

Deletion is the loss of a chromosomal segment; duplication is the repetition of a segment; inversion is the reversal of a segment; and translocation is the movement of a segment to a non-homologous chromosome.

What is pleiotropy and what is a human example?

Pleiotropy is when a single gene has multiple phenotypic effects; sickle-cell disease is a human example.

What is epistasis?

Epistasis is a type of gene interaction where one gene alters the phenotypic expression of another gene, such as hair color in Labrador retrievers.

What is polygenic inheritance, and what are two human examples?

Polygenic inheritance is the additive effect of two or more genes on a single phenotypic character; skin color and eye color are examples.

How can a test cross be used to determine an unknown genotype?

A test cross involves breeding an individual of unknown genotype showing a dominant phenotype with a homozygous recessive individual to see if any recessive offspring are produced.