Cell Biology: Chromosome Structure and Cell Cycle

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Questions and Answers

What is the main characteristic of polygenic inheritance?

The trait is always dominant.

Environmental factors have no influence.

Multiple genes contribute to the trait. (correct)

A single gene controls the trait.

What is the result of incomplete dominance?

The trait is always recessive.

The heterozygote has a phenotype that is a mixture of both alleles. (correct)

One allele is completely dominant.

The heterozygote has a phenotype that is the same as one of the homozygotes.

What determines an individual's blood type?

The presence or absence of the Rh factor.

The individual's diet and lifestyle.

The individual's genetic makeup and environmental factors.

The presence or absence of antigens A and B. (correct)

What is the term for the expression of both alleles in a heterozygote?

Codominance. Signup and view all the answers

What is the risk of transfusing blood with incompatible Rh types?

A severe and potentially life-threatening reaction. Signup and view all the answers

What is the term for the process by which the immune system produces antibodies against the Rh+ cells of a fetus?

Sensitization. Signup and view all the answers

What is the role of the Punnett square in genetics?

To predict the probability of inheritance of a trait. Signup and view all the answers

What is the term for the interaction between multiple genes and environmental factors?

Multifactorial inheritance. Signup and view all the answers

Who is considered the 'Father of Modern Genetics'?

Gregor Mendel Signup and view all the answers

What did Rosalind Franklin contribute to the understanding of DNA?

Used X-ray diffraction to capture images of DNA Signup and view all the answers

Which of the following is NOT a characteristic of the DNA double helix?

Uniform width throughout the molecule Signup and view all the answers

What is the primary function of DNA?

To store and transmit genetic information Signup and view all the answers

What is the process of DNA replication?

The duplication of the DNA molecule before cell division Signup and view all the answers

Which enzyme is responsible for breaking the hydrogen bonds between DNA strands during replication?

Helicase Signup and view all the answers

What is the significance of the antiparallel nature of DNA strands?

It enables DNA polymerase to synthesize new strands in opposite directions Signup and view all the answers

How does the genetic variation contribute to the diversity of life?

Genetic variation increases the diversity of life Signup and view all the answers

What is the name of the process by which a cell divides to produce two genetically identical daughter cells?

Mitosis Signup and view all the answers

Which phase of the cell cycle is responsible for the growth and replication of DNA?

S Signup and view all the answers

What is the role of cyclins and cyclin-dependent kinases in the cell cycle?

They control the timing of the cell cycle. Signup and view all the answers

Which of the following is NOT a checkpoint in the cell cycle?

Between prophase and metaphase Signup and view all the answers

What is the function of the nucleosomes in the packaging of DNA?

They help to condense the DNA into a more compact form. Signup and view all the answers

What is the main function of mitosis?

To create new cells for growth and development Signup and view all the answers

Which of the following is NOT a characteristic of eukaryotic chromosomes?

They are found in the cytoplasm of the cell. Signup and view all the answers

What is the difference between haploid and diploid cells?

Haploid cells have one set of chromosomes, while diploid cells have two sets of chromosomes. Signup and view all the answers

What is the main role of messenger RNA (mRNA)?

Carries genetic information from DNA to ribosomes. Signup and view all the answers

Where does transcription occur in the cell?

In the nucleus. Signup and view all the answers

During translation, what does the ribosome do with the mRNA?

It reads the nucleotide sequence to construct proteins. Signup and view all the answers

What does it mean that the genetic code is redundant?

One amino acid corresponds to multiple codons. Signup and view all the answers

What is the purpose of transfer RNA (tRNA) during protein synthesis?

It carries amino acids to the ribosomes. Signup and view all the answers

Which of these syndromes is characterized by a deletion in chromosome 5?

Cri-du-chat syndrome Signup and view all the answers

According to Mendel's law of segregation, what happens during gamete formation?

Alleles are separated so that each gamete gets one allele. Signup and view all the answers

What defines a dominant allele?

It is always expressed in the phenotype, regardless of the other allele. Signup and view all the answers

What is the chromosomal abnormality in Klinefelter syndrome?

Presence of an extra X chromosome Signup and view all the answers

Which of the following syndromes is caused by a trisomy?

Edwards syndrome Signup and view all the answers

What distinguishes Mendelian inheritance from non-Mendelian inheritance?

Mendelian inheritance follows strict laws formulating patterns of inheritance. Signup and view all the answers

What is a translocation in terms of chromosomal abnormalities?

Transfer of a segment of one chromosome to another non-homologous chromosome Signup and view all the answers

Which of these syndromes is associated with a characteristic cat-like cry?

Cri-du-chat syndrome Signup and view all the answers

What is the chromosomal abnormality in Turner syndrome?

Monosomy X Signup and view all the answers

Study Notes

Sexual Cells and Chromosome Structure

Human sex cells (gametes) are haploid, containing one set of chromosomes.
Eukaryotic chromosomes consist of a single double-helix of DNA.
DNA wraps around proteins called histones, forming nucleosomes that compact DNA to reduce its length.
Protein structures further coil the nucleosomes into larger configurations, resembling springs.
During cell division, additional proteins compact chromosomes for preparation.

Cell Cycle in Eukaryotes

Comprises two main phases: Interphase and Cell Division.
Interphase has three stages:
- G1 (Growth): Cells grow, some specialize and may either divide or remain specialized.
- S (Synthesis): DNA replication occurs alongside further growth.
- G2 (Preparation): Final preparations for mitosis.
Mitosis predominates in eukaryotic cell divisions, with meiosis occurring mainly in reproductive cells.

Regulation of the Cell Cycle

Controlled by cyclins and cyclin-dependent kinases (CDKs).
Checkpoints exist at:
- G1 to S phase
- G2 to M phase
- Between metaphase and anaphase
Ensures DNA integrity and proper chromosome organization.

Mitosis

A type of cell division producing two genetically identical daughter cells.
Responsible for growth and repair in organisms by replacing old cells.

Genetic Understanding and History

Mendel established the foundation of genetics through pea plant experimentation.
Thomas Hunt Morgan studied fruit flies and identified sex chromosomes.
Rosalind Franklin contributed critical X-ray diffraction images for DNA structure.
Watson and Crick expanded on these findings, contributing to the Human Genome Project mapping the human genome.

DNA Double Helix Model

Characterized by a helical structure and base complementarity: Adenine, Thymine, Cytosine, and Guanine.
Antiparallel strands running 5’ to 3’ and 3’ to 5’.
Comprised of nucleic acid, sugar, and nitrogenous bases.

DNA Significance

Stores genetic information guiding protein synthesis and cellular functions.
Replication ensures each daughter cell receives an accurate copy of DNA.

Protein Synthesis

Involves two main processes:
- Transcription occurs in the nucleus, where DNA is copied into mRNA.
- Translation happens in ribosomes, where mRNA is decoded to synthesize proteins using tRNA for amino acid transport.

Genetic Code

Organized in triplets (codons); universal across all living organisms.
Features include redundancy, clarity (no ambiguity), and specific start (AUG) and stop signals.

Mendelian Laws of Inheritance

Segregation: Each individual has two alleles; they segregate during gamete formation.
Independent Assortment: Inheritance of one allele does not affect another.
Dominance: Dominant alleles mask the effects of recessive alleles.

Types of Heredity

Mendelian inheritance follows Mendel's principles.
Non-Mendelian inheritance features complex gene interactions or environmental influences.

Probability Calculations in Genetics

Punnett squares predict possible genotypes and phenotypes from parental genotypes.

Advanced Genetic Concepts

Polygenic traits: Multiple genes affect a single phenotype, leading to continuous variation.
Multifactorial inheritance: Interaction of multiple genes and environmental factors impacts traits.

Human Blood Groups and Inheritance

Blood type is determined by the presence of antigens (A and B).
Codominance occurs when both alleles express equally; blood types include A, B, AB (universal recipient), and O (universal donor).
Rh factor determines blood type as positive (dominant) or negative (recessive).

Genetic Disorders and Chromosomal Aberrations

Trisomy and monosomy conditions (e.g., Down syndrome, Turner syndrome).
Structural changes in chromosomes can lead to severe genetic disorders through deletions, duplications, inversions, and translocations.

Additional Genetic Disorders

Turner syndrome: Affects females with partial or complete absence of an X chromosome.
Klinefelter syndrome: Affects males characterized by an additional X chromosome, leading to infertility and development issues.
Cri du chat syndrome: Result of deletion in chromosome 5, causing distinctive crying sounds and developmental disabilities.

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Description

Learn about the structure of sexual cells, chromosome composition, and the process of cell division in eukaryotes. Explore how DNA wraps around histones, forming nucleosomes and compacting chromosomes.