DNA Structure and Chromosomes Quiz

Questions and Answers

How many chromosomes do humans have in total, and why are they in pairs?

46 chromosomes, because they result from mitosis

46 chromosomes, to ensure genetic diversity (correct)

46 chromosomes, as pairs facilitate cell division

23 chromosomes, to maintain chromosome symmetry

What is the primary purpose of mitosis?

To enable growth and tissue repair (correct)

To generate gametes for sexual reproduction

To produce mutations for adaptation

To create genetic diversity via recombination

Which of the following correctly describes a dominant allele?

An allele that masks the expression of a recessive allele (correct)

An allele that is only expressed in homozygous conditions

An allele that is always inherited on the X chromosome

An allele that influences traits only in females

What type of mutation involves the addition of one or more nucleotides to the DNA sequence?

<p>Insertion</p> Signup and view all the answers

In a Punnett square, what does the term 'heterozygous' refer to?

<p>Having two different alleles for a trait</p> Signup and view all the answers

Study Notes

DNA Structure and Characteristics

DNA (deoxyribonucleic acid) is a double helix structure composed of nucleotide units.
Nucleotides consist of a sugar, phosphate group, and nitrogenous base.
The four nitrogenous bases are adenine (A), thymine (T), cytosine (C), and guanine (G), which form complementary base pairs: A-T and C-G.
DNA is organized into structures called chromosomes.

Chromosomes and Human Count

Humans have 46 chromosomes arranged in 23 pairs.
Each pair consists of one chromosome from each parent, providing genetic diversity and redundancy.
22 pairs are autosomes, and the 23rd pair consists of sex chromosomes (XX in females, XY in males).

Karyotypes and Chromosomal Composition

A karyotype is a visual representation of an individual's chromosomes used to identify chromosomal abnormalities.
Diploid (2n) refers to cells with two sets of chromosomes (46 in humans), while haploid (n) cells have one set (23).

Genetic Inheritance

Alleles are different versions of a gene that can exist at the same locus.
Dominant alleles mask the expression of recessive alleles; a dominant trait appears in the phenotype if at least one dominant allele is present.
Punnett squares can be used to predict the probability of inheriting certain traits based on parental genotypes.

Genotypes, Phenotypes, and Sex-linked Traits

Genotype refers to the genetic constitution of an individual (e.g., BB, Bb, bb), while phenotype is the observable physical or biochemical characteristics.
Sex-linked characteristics are traits associated with genes located on sex chromosomes, often affecting males more due to the presence of a single X chromosome.

Mutations and Their Types

Mutations are changes in the DNA sequence that can affect gene function and traits.
Types of mutations include:
- Substitutions: Replacement of one nucleotide with another.
- Deletions: Removal of one or more nucleotides.
- Insertions: Addition of one or more nucleotides.
- Inversions: Reversal of a sequence of nucleotides.
Mutations can arise from errors during DNA replication, environmental factors, or chemical exposure.

Genetic Processes

Transcription: The process where DNA is copied into messenger RNA (mRNA).
Translation: The conversion of mRNA into a protein at the ribosome.

Mitosis Overview

Mitosis is the process of cell division that results in two identical daughter cells, crucial for growth, development, and maintenance.
Interphase: The preparatory phase before mitosis, where the cell grows and DNA replicates.
Mitosis consists of four main phases:
- Prophase
- Metaphase
- Anaphase
- Telophase
The purpose of mitosis is to ensure the equal distribution of genetic material to daughter cells, maintaining the original cell’s genetic identity.

Description

Test your knowledge on DNA structure, human chromosomes, and genetic inheritance! This quiz covers the characteristics of DNA, the organization of chromosomes in humans, and the concepts of karyotypes and genetic diversity. Challenge yourself and deepen your understanding of genetics.