Biology Practice Flashcards: Meiosis, Inheritance, and Evolution

Exactly 250 vocabulary-style flashcards covering Meiosis, Inheritance Patterns, and Evolutionary Patterns/Mechanisms based on the provided lecture transcript.

Gametes

Sex cells (sperm and egg) that contain one set of chromosomes (haploid).

Fertilization

The fusion of two gametes to form a diploid zygote.

Diploid ($2n$)

A cell containing two sets of chromosomes, one from each parent.

Haploid ($n$)

A cell containing one set of chromosomes.

Homologous Pairs of Chromosomes

Two chromosomes that carry the same genes but may have different alleles; one inherited from each parent.

Sister Chromatids

Identical copies of a chromosome joined at the centromere.

Meiosis I

The first division of meiosis in which homologous chromosomes separate.

Prophase I

Phase where homologous chromosomes pair up and crossing over occurs.

Metaphase I

Phase where homologous chromosome pairs line up at the cell's equator.

Anaphase I

Phase where homologous chromosomes separate.

Telophase I

Phase where two haploid cells form.

Meiosis II

The second division of meiosis, similar to mitosis, in which sister chromatids separate.

Prophase II

Phase where chromosomes condense and spindle fibers form.

Metaphase II

Phase where chromosomes line up individually in the center.

Anaphase II

Phase where sister chromatids separate.

Telophase II

Phase where four haploid cells form.

Sexual Reproduction

Reproduction involving the fusion of gametes from two parents.

Crossing Over

Exchange of DNA between homologous chromosomes during Prophase I.

Recombinant Chromosomes

Chromosomes containing DNA from both homologous chromosomes after crossing over.

Independent Assortment

Random orientation of homologous chromosome pairs during Metaphase I.

Nondisjunction

Failure of chromosomes to separate properly during meiosis.

Genetic Diversity

Variation in genetic traits among individuals.

Chromosome Map

A diagram showing relative gene positions based on crossing-over frequency.

Reduction Division

The process of meiosis I that reduces chromosome number from diploid ($2n$) to haploid ($n$).

Human body cell chromosome count

46 chromosomes.

Human gamete chromosome count

23 chromosomes.

Somatic cells

Body cells that are diploid ($2n$).

Synapsis

The process during Prophase I where homologous chromosomes pair up.

Cytokinesis

The cell division step that occurs during Telophase I and Telophase II.

Equational division

Another name for Meiosis II because it does not further reduce the chromosome number.

Trisomy

A condition where a zygote has an extra chromosome ($n+1$) after fertilization.

Monosomy

A condition where a zygote is missing a chromosome ($n-1$) after fertilization.

Down syndrome

A specific example of Trisomy 21 caused by nondisjunction.

Random Fertilization diversity calculation (Humans)

8.4 million sperm combinations $\times$ 8.4 million egg combinations = ~70 trillion possibilities.

Independent Assortment combinations (Humans)

$2^{23}$ or approximately 8.4 million possible combinations.

Number of divisions in Mitosis

1 division.

Number of divisions in Meiosis

2 divisions.

Daughter cells in Mitosis

2 daughter cells.

Daughter cells in Meiosis

4 daughter cells.

Genetic relationship of Mitosis daughter cells

Genetically identical.

Genetic relationship of Meiosis daughter cells

Genetically different.

End product of Mitosis

Diploid to Diploid.

End product of Meiosis

Diploid to Haploid.

Primary purpose of Mitosis

Growth and repair.

Primary purpose of Meiosis

Gamete production.

Allele segregation time

Alleles segregate during Anaphase I of meiosis.

Source of new allele combinations

Crossing over.

Close gene proximity effect

Genes crossover less frequently.

Distant gene proximity effect

Genes crossover more frequently.

Genotype

The genetic makeup (allele combination) of an organism.

Phenotype

The observable trait produced by a genotype.

Allele

A different version of a gene.

Gene

A segment of DNA that codes for a specific trait or protein.

Homozygous

Having two identical alleles (e.g., BB or bb).

Heterozygous

Having two different alleles (e.g., Bb).

Dominant Allele

An allele expressed whenever it is present, masking the recessive allele.

Recessive Allele

An allele expressed only when two copies are present.

Law of Segregation

The principle that two alleles for a trait separate during gamete formation.

Law of Independent Assortment

The principle that genes on different chromosomes assort independently during meiosis.

Principle of Dominance

In a heterozygote, the dominant allele masks the recessive allele.

Incomplete Dominance

Neither allele is completely dominant, producing an intermediate (blended) phenotype.

Codominance

Both alleles are fully expressed simultaneously.

X-Linked Trait

A trait controlled by a gene on the X chromosome.

Multiple Alleles

A gene with more than two possible alleles in a population (e.g., ABO blood group).

Polygenic Trait

A trait controlled by multiple genes, resulting in a wide range of phenotypes.

Epistasis

One gene affects or masks the expression of another gene.

Punnett Square

A diagram used to predict offspring genotypes and phenotypes.

Pedigree

A family tree used to track inheritance patterns.

Incomplete Dominance example

Red flower $\times$ White flower = Pink flower.

Codominance example

AB blood type.

Multiple Alleles example

ABO blood group.

Polygenic trait examples

Height, skin color, and eye color.

Epistasis example

Coat color pathways where a pigment gene blocks another color gene.

X-linked trait examples

Color blindness and Hemophilia.

Pedigree symbol: Square

Male.

Pedigree symbol: Circle

Female.

Pedigree symbol: Filled shape

Affected individual.

Pedigree symbol: Half-filled shape

Carrier.

Monohybrid Genotype Ratio ($Bb \times Bb$)

$1:2:1$ ($1$ BB, $2$ Bb, $1$ bb).

Monohybrid Phenotype Ratio ($Bb \times Bb$)

$3:1$ ($3$ dominant, $1$ recessive).

Dihybrid Phenotype Ratio ($RrYy \times RrYy$)

$9:3:3:1$.

Genotype $I^{A}I^{A}$ or $I^{A}i$ phenotype

Blood Type A.

Genotype $I^{B}I^{B}$ or $I^{B}i$ phenotype

Blood Type B.

Genotype $I^{A}I^{B}$ phenotype

Blood Type AB.

Genotype $ii$ phenotype

Blood Type O.

Reason males express X-linked recessive traits more often

Males only have one X chromosome.

Mendelian Inheritance limit

Inheritance is often more complex because of incomplete dominance, codominance, etc.

Fossil

Preserved remains, impressions, or traces of ancient organisms.

Relative Dating

Determining if a fossil is older or younger based on rock layer position.

Law of Superposition

Oldest layers are at the bottom and youngest layers are at the top in undisturbed rock.

Radiometric Dating

Determining the absolute age of rocks or fossils using radioactive decay.

Homologous Structures

Structures with similar anatomy due to common ancestry, even with different functions.

Vestigial Structures

Reduced or unused structures inherited from ancestors.

Analogous Structures

Structures with similar functions but different evolutionary origins.

Biochemical Evidence

Evidence from DNA, RNA, and protein sequences used to determine relationships.

Phylogenetic Tree

A branching diagram showing evolutionary relationships among organisms.

Cladogram

A diagram grouping organisms according to shared derived characteristics.

Derived Characters

Traits that evolved in a recent common ancestor and are shared by descendants.

Fossil formation step 1

Organism dies.

Fossil formation step 2

Quickly buried by sediment.