Cell Cycle and Nucleic Acids Overview

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Questions and Answers

What describes the purpose of Mendel's hybridization process?

To observe traits in different species.

To strictly control mating between plants. (correct)

To mix all traits randomly.

To enhance growth rate of plants.

Which statement accurately reflects the law of segregation?

Alleles separate during the formation of gametes. (correct)

Only one allele is passed on to the offspring.

Two alleles for a character are inherited independently.

Alleles are blended together during fertilization.

What is the correct definition of an allele?

An alternative version of a gene. (correct)

A location on a chromosome.

A specific gene of an organism.

The physical appearance of a trait.

Which of the following pairs best explains genotype versus phenotype?

Genotype is the genetic makeup; phenotype is the observable trait. Signup and view all the answers

How does crossing over contribute to genetic variation?

By producing new combinations of alleles. Signup and view all the answers

What mechanism contributes to genetic variation through the random combination of gametes?

Independent assortment of chromosomes. Signup and view all the answers

Which of these scenarios is an example of codominance?

A flower that exhibits both purple and white spots. Signup and view all the answers

What does the term 'locus' refer to in genetics?

The location of a gene on a chromosome. Signup and view all the answers

Which of these describes a scenario involving incomplete dominance?

A red and white flower generation produces pink flowers. Signup and view all the answers

Why is Mendel's work with peas significant for understanding genetics?

Peas have traits that are easily distinguishable and controllable. Signup and view all the answers

What does the law of segregation state regarding alleles during gamete formation?

Alleles separate and end up in different gametes. Signup and view all the answers

In a genetic cross where purple-flower (P) is dominant over white-flower (p), what would be the expected phenotype ratio from a Pp x Pp cross?

3 purple : 1 white Signup and view all the answers

What is the primary distinction between homozygous and heterozygous organisms?

Homozygous organisms have identical alleles, while heterozygous organisms have different alleles. Signup and view all the answers

What do the terms phenotype and genotype refer to in genetics?

Phenotype represents an organism's physical appearance, while genotype refers to its genetic makeup. Signup and view all the answers

When performing a dihybrid cross, how do you calculate the probabilities of different genotypes?

By multiplying the individual probabilities of each character. Signup and view all the answers

What is the term for when one allele hides the presence of another allele in a heterozygote?

Complete dominance Signup and view all the answers

Which of the following describes traits that are influenced by more than one gene?

Polygenic inheritance Signup and view all the answers

In pedigree analysis, what does a circle represent?

A female Signup and view all the answers

What do we call the genetic makeup of an organism?

Genotype Signup and view all the answers

Which of these disorder types requires an individual to be homozygous for the allele to express the trait?

Recessively inherited disorders Signup and view all the answers

Which genetic model describes the situation where two dominant alleles affect the phenotype in separate ways?

Codominance Signup and view all the answers

What does X-inactivation result in within female mammals that are heterozygous for a gene located on the X chromosome?

It ensures only one X chromosome is expressed. Signup and view all the answers

In humans, what must be true for a male to express a recessive X-linked trait?

He must inherit one copy of the allele. Signup and view all the answers

What occurs when one gene impacts the expression of another gene's phenotype?

Epistasis Signup and view all the answers

Which scenario illustrates incomplete dominance?

A red flower and a white flower producing pink flowers. Signup and view all the answers

Which of the following describes the principle that Mendelian genes segregate independently during gamete formation?

Law of independent assortment Signup and view all the answers

What is a characteristic feature of a recessively inherited disorder?

Affected individuals are generally homozygous for the allele. Signup and view all the answers

What is the significance of the locus where a gene is found on a chromosome?

It is the physical location of a gene on a chromosome. Signup and view all the answers

Study Notes

The Cell Cycle

A polypeptide's amino acid sequence is programmed by a gene, which is made of DNA.
DNA is a nucleic acid made of nucleotides.
Nucleic acids come in two types: DNA and RNA.
DNA provides instructions for its replication.
Nucleic acids are polymers called polynucleotides.
Each polynucleotide is made of monomers called nucleotides.
A nucleotide consists of a nitrogenous base, a pentose sugar, and one or more phosphate groups.
There are two families of nitrogenous bases: pyrimidines (single ring) and purines (double ring).
Pyrimidines include cytosine, thymine, and uracil.
Purines include adenine and guanine.
Thymine is found only in DNA, and uracil is found only in RNA.
The sugar in DNA is deoxyribose; in RNA, it is ribose.
DNA has thymine; RNA has uracil.
Adjacent nucleotides are joined by a phosphodiester linkage.
DNA is a double helix with two polynucleotides spiraling around an imaginary axis.
The two backbones in DNA run in opposite directions (antiparallel).
DNA molecules are typically long, with thousands or millions of base pairs.
Adenine pairs with thymine; guanine pairs with cytosine.

Somatic vs. Gamete Cells

Gamete cells are reproductive cells.
Somatic cells are any cell of a living organism other than reproductive cells.

Cell Division

Cell division allows organisms to produce more of their kind.
In unicellular organisms, cell division reproduces the entire organism.
In multicellular eukaryotes, cell division enables development, renewal, and repair.
DNA is passed down from one cell generation to the next with remarkable accuracy.

Cell Cycle Summary

Interphase (chromosome copying): G1 phase, S phase, G2 phase.
Mitosis (chromosome division).
Cytokinesis (cell division).
The cell cycle's phases are Prophase, Prometaphase, Metaphase, Anaphase, and Telophase. The Phases are abbreviated by P-P-M-A-T

Mitotic Spindle

The mitotic spindle is made of microtubules and associated proteins.
It controls chromosome movement during mitosis.
The centrosome is a microtubule-organizing center (in animal cells).
Spindle microtubules grow out from the centrosomes.

Binary Fission

Prokaryotes reproduce via binary fission.
The single chromosome replicates.
The two daughter chromosomes separate as the cell elongates.
The plasma membrane pinches inward, dividing the cell into two.

Sexual vs. Asexual Reproduction

Asexual reproduction produces genetically identical offspring (clones).
Sexual reproduction involves the fusion of gametes from two parents, creating genetically diverse offspring.

Chromosome Sets in Human Cells

Human somatic cells have 23 pairs of chromosomes (46 total).
A karyotype is an ordered display of the homologous pairs of chromosomes.
Homologous chromosomes are the same length and shape, carrying the same genes.
The sex chromosomes are called X and Y. Females have XX, males have XY.
The remaining 22 pairs are called autosomes.
A diploid cell has two sets of chromosomes (2n); in humans, 2n=46.
A haploid cell has one set of chromosomes (n); in humans, n=23.

The Human Life Cycle

Meiosis and fertilization alternate to maintain chromosome number in sexually reproducing organisms.
The three types of sexual life cycles differ in timing of meiosis and fertilization.

Haploid-Dominant Life Cycle

In some fungi and algae, the multicellular organism is haploid.
The zygote is the only diploid stage.
Haploid cells grow into multicellular forms through mitosis, which produce gametes through mitosis.

Alternation of Generations

Plants and some algae have both diploid and haploid multicellular stages.
The diploid stage, called the sporophyte, produces haploid spores by meiosis.
These spores grow into haploid multicellular forms called gametophytes that produce gametes via mitosis.
Fertilization of the gametes produces a diploid sporophyte, completing the life cycle.

Origins of Genetic Variation Among Offspring

Independent assortment of chromosomes.
Crossing over.
Random fertilization

The Stages of Meiosis

Meiosis I separates homologous chromosomes.
Meiosis II separates sister chromatids as in mitosis but resulting in haploid cells.
Crossing over and synapsis during prophase I.
Four haploid cells are produced at the end of meiosis.
Meiosis reduces the number of chromosome sets from two to one per gamete.

Mendel's Experiments

Mendel's experiments on pea plants led to principles of inheritance.
He studied contrasting traits in pea plants.
He followed the inheritance of these traits across generations.

Mendel’s Laws

Law of Segregation.
Law of Independent Assortment.
Heterozygous vs Homologous

Genetic Vocabulary

Homozygous - Two identical alleles for a particular gene.
Heterozygous - Two different alleles for a particular gene
Phenotype- Observable physical traits.
Genotype - Genetic Makeup.

Incomplete Dominance

The heterozygote's phenotype is intermediate between the homozygotes'.
Example: pink flowers from red and white parent flowers.

Multiple Alleles

More than 2 alleles exist for a given gene.

Polygenic Inheritance

More than one gene affects a phenotype trait.

Nature vs Nurture

Phenotypes determined by both genetic factors and environmental factors.

Recessively Inherited Disorders

Many genetic diseases are inherited recessively.
Recessive disorders appear only in individuals homozygous for the recessive allele.
Carriers are heterozygous for the disorder, but they show no traits.

Pedigree Analysis

Pedigree analysis tracks traits across family members.
Pedigree patterns provide clues to inheritance mode.

Sex-Linked Inheritance

Some genes are located on sex chromosomes.
Males have one X and one Y; females have two X's.
X-linked traits show different patterns in males and females.
Examples of X-linked traits are Red-green colorblindness, and Duchene muscular dystrophy.

Sex Determination and Chromosome Structure

X-inactivation in female mammals, one of the two X chromosomes in each cell is randomly inactivated.
Chromosome structure changes can alter phenotype.
Genetic disorders can arise from changes in chromosome number or structure.

Chromosome Alterations and Disorders

Large-scale chromosomal alterations often lead to developmental disorders.
Aneuploidy, a change in the number of chromosomes.
Polyploidy, more than two sets of chromosomes.

Other Important Considerations

Environmental factors influence the expression of genetic traits.
Genetic and environmental factors are involved in many diseases.

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Description

This quiz focuses on the cell cycle and the structure of nucleic acids, including DNA and RNA. It covers the composition of nucleotides, the differences between pyrimidines and purines, and the characteristics of DNA and RNA. Test your understanding of these fundamental biological concepts.