Campbell Biology Unit 5-Heredity Concepts

What are the phases of meiosis 1?

Prophase 1, Metaphase 1, Anaphase 1, and Telophase 1

What are the phases of meiosis II?

prophase 2, metaphase 2, anaphase 2, and telophase 2

What is the role of meiosis 1?

The role of meiosis 1 is to separate homologous chromosomes, transforming the cell from a diploid state to a haploid state

What is the role of meiosis 2?

The role of meiosis 2 is to separate the sister chromatids and segregate them to different daughter cells

What happens in prophase 1?

Centrosome movement, spindle formation, and nuclear envelope breakdown occur as in mitosis. Each chromosome pairs with its homologous pair begins crossing over, and microtubules from one pole attach to the kinetochores

What happens in prophase 2?

A spindle apparatus forms. Chromosomes associated at the centromere are moved by microtubules.

What happens in metaphase 1?

Pairs of homologs chromosomes are arranged at the metaphase plate, with one chromosome of each pair facing each pole

What happens in metaphase 2?

Chromosomes are positioned at the metaphase plate. The kinetochores of sister chromatids are attached to microtubules extending from opposite poles.

What happens in anaphase 1?

Breakdown of proteins that are responsible for sister chromatid cohesion. The homologs move towards the opposite poles, guided by the spindle apparatus, and sister chromatid cohesion persists at the centromere, causing chromatids to move as a unit towards the same pole

What happens in anaphase 2?

Breakdown of proteins holding the sister chromatids together at the centromere allows the chromatids to separate.

What happens in telophase and cytokinesis 1?

Each half of the cell has a completed haploid set of duplicated chromosomes. This coincides with the formation two haploid daughter cells. No chromosome duplication occurs between meiosis 1 and 2

What happens in telophase and cytokinesis 2?

Nuclei form, the chromosomes begin decondensending, and cytokinesis occurs

Describe the daughter cells resulting from mitosis.

As a result of mitosis, there are two daughter cells which are each genetically identical to the parent cell with the same number of chromosomes

Describe the daughter cells resulting from meiosis.

As a result of meiosis, there are four haploid daughter cells that are genetically different from the parent cell and from each other

When do homologous chromosomes separate during meiosis?

Homologous chromosomes are separated during anaphase 1, where the cell turns from diploid to haploid

How do homologous chromosomes separate during anaphase?

The sister chromatids remain attached to the kinetochore microtubules, and the centrosome pulls the sister chromatids towards opposite poles.

How do daughter cells receive both maternal and paternal chromosomes?

Daughter cells receive both maternal and paternal chromosomes because of random assortment and crossing over.

What is crossing over?

Where the DNA molecules of non sister chromatids are broken and rejoined to each other

How does crossing over increase genetic diversity?

Crossing over produces recombinant genes (individual chromosomes that carry genes from two different parents) and chromosomes that carry genes from two different parents.

What is independent assortment?

Two or more genes assort independently, each pair of alleles segregates independently of any other pair of alleles during gamete formation

How does independent assortment increase genetic diversity?

Due to independent assortment, there are 8.4 million possible chromosome combinations in each male and female gamete.

How does segregation lead to genetic variation?

The law of segregation ensures that each gamete receives only one allele for each gene, creating a wide range of possible allele combinations.

What is random fertilization?

The random chance of the union of gametes, culminating in fusion of their nuclei.

How does random fertilization increase genetic diversity?

Random fertilization increases genetic diversity because due to random fertilization, there are 70 trillion diploid combinations possible.

What organisms have ribosomes? How does that demonstrate common ancestry?

All organisms have ribosomes, regardless if the organism is prokaryotic or eukaryotic. This demonstrates common ancestry because it shows all life came from a common ancestor.

How does a shared genetic code demonstrate common ancestry?

A shared genetic code across all organism demonstrates that all life came from a common ancestor.

What metabolic process do all organisms undergo which demonstrates common ancestry?

All organisms undergo glycolysis (cellular respiration)

What is the law of independent assortment?

Two or more genes assort independently, each pair of alleles segregates independently of any other pair of alleles during gamete formation

What is the law of segregation?

The two alleles for a heritable character segregate (separate) during gamete formation and end up in different gametes, ensuring that each gamete receives only one allele for each gene

What is the expected ratio of a monohybrid cross based on Mendel's laws? (Genotype and Phenotype)

Phenotype: 3:1 (dominant to recessive)

Genotype: 1:2:1 (homozygous dominant to heterozygous to homozygous recessive)

What is the expected ratio of a dihybrid cross based on Mendel's laws? (phenotype)

Phenotype: 9:3:3:1 (Dominant to dominant recessive to recessive dominant to recessive)

What are the parent's genotype if the F1 ratio is 1:1?

One parent is heterozygous and the other parent is homozygous recessive.

What is complete dominance?

When an allele caused a F1 offspring to always look like one parental variety over the other

What is incomplete dominance?

When neither allele is completely dominant, and the F1 hybrids have a phenotype somewhere between those of the two parental varieties.

What is codominance?

When two alleles each affect the phenotype in separate, distinguishable ways.

How are the phenotypic and genotypic ratios of a monohybrid cross different in incomplete dominance?

Phenotype: 1:2:1 (homozygous dominant to heterozygous to homozygous recessive)

Genotype: 1:2:1 (homozygous dominant to heterozygous to homozygous recessive)

How are the phenotypic and genotypic ratios of a monohybrid cross different in codominance?

Phenotype: 1:2:1 (homozygous dominant to heterozygous to homozygous recessive)

Genotype: 1:2:1 (homozygous dominant to heterozygous to homozygous recessive)

How are the phenotypic and genotypic ratios of a monohybrid cross different in complete dominance?

Phenotype: 3:1 (dominant to recessive)

Genotype: 1:2:1 (homozygous dominant to heterozygous to homozygous recessive)

What are linked genes?

Genes located near each other on the same chromosome that tend to be inherited together in genetic crosses.

How are the predicted ratios different in linked genes?

Linked genes will produce genes where parental phenotypes are more common, while recombinant genotypes are less common, swaying away from the traditional Mendelian ratios.

What is a polygenic trait?

A characteristic controlled by multiple genes and/or influenced by the environment

What organelles contain DNA? How does this support the endosymbiotic theory?

The nucleus, mitochondria, and chloroplast. This supports the endosymbiotic theory because it states an early ancestor of eukaryotic cells engulfed a double membraned prokaryote, which are now the mitochondria and chloroplast.

What would you look for in a pedigree to identify if the trait is dominant or recessive?

If the trait is dominant, the trait would occur in every generation, including the parents. If the trait is recessive, the trait may skip a few generations.

What would you look for in a pedigree to identify if the trait is autosomal or sex-linked?

If the trait is autosomal, the trait would roughly affect equal amounts of male and females. If the trait is sex linked, the trait would affect more of one population than the other.

What would you look for in a pedigree to identify if the trait is due to non-nuclear inheritance?

A trait would be due to non-nuclear inheritance if the trait is passed down from all mothers to their offspring.

How do environmental factors affect gene expression?

Environmental factors can lead to phenotype plasticity.

What occurs during segregation in meiosis, and what phase does it take place in?

During meiosis, anaphase 1 is when segregation begins, and during anaphase 1, the two homologous chromosomes separate, ensuring that each gamete receives only one allele per gene.

What is phenotype plasticity?

The ability of an organism to express different phenotypes in response to environmental variations.

What occurs during independent assortment in meiosis, and what phase does it take place in?

Independent assortment occurs in metaphase 1 when pairs of homologous chromosomes randomly face a direction, creating genetic diversity.

What is the chromosomal basis of inheritance?

Mendelian genes have specific loci (positions) along chromosomes and it is the chromosomes that undergo segregation and independent assortment

What is nondisjunction?

Where the members of a pair of homologous chromosome don't move apart properly during meiosis 1 or sister chromatids fail to separate during meiosis 2.