Meiosis, Sexual Reproduction, and Mendelian Genetics Flashcards

Flashcards based on lecture notes covering Meiosis, Sexual Reproduction, Mendelian Genetics, and Gene Expression.

What type of chromosomes are pairs 1-22 in humans?

Autosomes

What are the sex-determining chromosomes in humans?

Sex chromosomes (X and Y)

How many chromosomes do humans have in total?

46

What occurs during meiosis I?

Homologous pairs separate

What is ploidy a measure of?

Number of sets of chromosomes

What connects sister chromatids?

Centromere

What process reduces a diploid cell to a haploid cell?

Meiosis

What is the synaptonemal complex?

Where homologous chromosomes pair up and physically connect during prophase I

What is crossing over?

Exchange of genetic material by homologous chromosomes

What are recombinant chromosomes?

Chromosomes that carry gene combinations "mixed" from both parents

What are chiasmata?

Visible structures at cross over points

What is a tetrad?

Four chromatids held together by chiasmata

What is the diploid number in humans?

2n, 46

What is the haploid number in humans?

n, 23

During what phase are tetrads arranged at the cell equator?

Metaphase I

What contributes to genetic variation among gametes?

Independent Assortment, Segregation, and crossing over

What happens to homologous pairs during anaphase I?

Pulled apart by microtubules

How is the number of possible gamete combinations calculated?

2^n (n = # of chromosomes in a set)

What process occurs during prophase I of meiosis I?

Crossing over

During what phase do sister chromatids align at the metaphase plate in mitosis and meiosis II?

Metaphase II

What is the outcome of meiosis II?

Separation of sister chromatids

What does asexual reproduction produce?

Identical offspring (clones)

What is a major disadvantage of asexual reproduction?

Absolutely no variation

What does sexual reproduction involve?

Fusion of two gametes

What is the diploid-dominant life cycle?

Life cycle used by humans and most animals

Where are gametes produced?

Gonads (testes and ovaries)

What do testes produce?

Sperm

What do ovaries produce?

Eggs

What is a zygote?

Single-celled entity formed when a sperm cell fertilizes an egg cell

What are the two main processes responsible for genetic variation?

Meiosis and fertilization

How many sperm are produced per mL on average?

250,000,000

What type of cells are genetically identical and have the same number of chromosomes as the original cell?

Mitosis

What type of cells are non-genetically identical and have half the original number of chromosomes?

Meiosis

What are spermatogonia?

Diploid cells within the testes that become primary spermatocytes

What do primary spermatocytes undergo to form secondary spermatocytes?

Meiosis I

What do secondary spermatocytes undergo to form spermatids?

Meiosis II

What cells differentiate into spermatozoa?

Spermatids

What are oogonia?

2n cell in the outer cortex of ovary that becomes a primary oocyte

What does the primary oocyte undergo to produce a secondary oocyte and a polar body?

Meiosis I

What does the secondary oocyte undergo to form an ootid and polar body?

Meiosis II

What does the ootid differentiate into?

Ovum

Who discovered the basic principles of heredity?

Gregor Mendel

What plant did Mendel use for his experiments?

Pea plants

What two fundamental laws of genetics did Mendel identify?

Independent assortment and segregation

What does true-breeding mean?

Organisms that always pass down a specific phenotypic trait

What is hybridization?

Crossing two different true-breeding plants

What is Mendel's 1st Law?

The Law of Segregation

The Law of Segregation separates what?

Two alleles for a heritable characteristic

What is a character?

Heritable feature (flower color)

What is a trait?

Variation of a character (white/purple color)

What is a locus?

A specific location on a chromosome where a gene is located

What is the genetic makeup of an organism?

Genotype

What is the physical appearance of an organism?

Phenotype

What is Mendel's 2nd Law?

Independent Assortment

What does Mendel's 2nd Law state?

Alleles of unlinked genes assort independently

What is a dihybrid cross?

Cross involving two traits of interest

What is the phenotypic ratio of F2 generation in a dihybrid cross?

9:3:3:1

What is the multiplication rule?

The probability that two or more independent events will occur together

What is the addition rule?

The probability that any one of two mutually exclusive events will occur

What is complete dominance?

The phenotypes of the heterozygous and dominant homozygote are identical

What is codominance?

Two dominant alleles affect the phenotype in separate, but distinguishable, ways

What is incomplete dominance?

The phenotypes of F1 hybrids are somewhere between the phenotypes of the two parental varieties

What are lethal alleles?

Non-functional alleles that can kill the individual inheriting it

What is pleiotropy?

When a gene has multiple phenotypic effects

What are polygenic traits?

Traits determined by two or more genes

What is epistasis?

A gene at one locus alters the phenotypic expression of a gene at another locus

What does quantitative variation indicate?

Polygenic inheritance

What are multifactorial characteristics?

Phenotypes influenced by both genetics and environment

What is norm of reaction?

The phenotypic range of a particular genotype that is influenced by the environment

What does the Chromosome Theory of Inheritance state?

Mendelian genes have specific loci on chromosomes

Who provided evidence that chromosomes are the location of Mendel's heritable factors?

Thomas Hunt Morgan

What are wild type phenotypes?

"Normal" common phenotypes in the fly populations

Why is Morgan's research important?

It was the first solid evidence indicating that a specific gene is associated with a specific chromosome

Who observed that proper sea urchin embryonic development does not occur unless chromosomes are present?

Theodor Boveri

What is genetic linkage?

First demonstration that genes were located on chromosomes – T.H. Morgan’s fruit fly work

What do linked genes tend to do?

Be inherited together

What violates the law of independent assortment?

Genetic Linkage

What is the mechanism that segregates genes on the same chromosome?

Cross over between homologous chromosomes

What is the inheritance pattern of unlinked genes?

50% parental type and 50% recombinant offspring

What is the inheritance pattern of linked genes when no crossover occurs?

No recombinant offspring, all are parental type

What is recombination frequency?

The frequency with which a single chromosomal crossover will take place between two genes during meiosis

What is a linkage map?

A diagram of relative gene locations

What is a centimorgan?

Unit equal to one genetic map unit (gmu)

Which chromosome is shorter, 21 or 22?

Chromosome 21

What is nondisjunction?

When a cell has an abnormal chromosome number

What is aneuploidy?

Offspring have an abnormal # of a particular chromosome

What is polyploidy?

When there are more than 2 COMPLETE sets of chromosome in an organism

What is XIST?

X-inactive specific transcript

Why do male cats never exhibit a tortoise shell coat color?

Affects only female

Which syndrome is caused by Chromosome 21 having three chromosomes instead of two?

Trisomy 21 (Down Syndrome)

Nondisjunction in female XX affects which sex?

Affects only female

What is a human genetic disorder resulting from a chromosomal recombination mutation that causes a deletion of part of chromosome 5?

Cri-du-chat syndrome

What is a genetic mutation?

Any change in a DNA sequence

What is a point mutation?

The change of a single nucleotide in the template DNA

What change in a nucleotide results in a change to the amino acid?

Missense (Nonsynonymous) Substitution

What type of mutation causes the encoding of a premature stop codon?

Nonsense Substitutions

What are additions or losses of nucleotide pairs in a gene called?

Insertions or Deletions (Indels)

What do genes must be to dictate whether a cell is a muscle, liver, or nerve cell?

Regulated

What is cell differentiation?

A process of specialization in form and function that cells undergo

What are operons?

Clusters of genes that are transcribed together