Genetics and Inheritance: DNA, Chromosomes, and Mutations Study Guide

What are the parts that make up DNA?

DNA is made up of nucleotides, which consist of a phosphate group, a sugar (deoxyribose), and a nitrogenous base.

How is DNA structured?

DNA has a double helix structure formed by two strands of nucleotides twisted around each other.

Where is DNA stored in the cell?

DNA is stored in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells.

How is DNA formed?

DNA is formed through the process of DNA replication, where the double helix unwinds and each strand serves as a template for a new complementary strand.

Compare chromosomes, genes, and chromatin.

Chromosomes are structures made of DNA and proteins that contain genes; genes are segments of DNA that code for proteins; chromatin is the complex of DNA and protein found in the nucleus.

How does DNA replication occur and what are the results?

DNA replication occurs through unwinding of the double helix and complementary base pairing, resulting in two identical DNA molecules.

What are the two reasons how DNA results in different living things?

Different sequences of nucleotides in DNA lead to variations in genes, which produce different traits in organisms.

What are the four organic bases in DNA?

The four organic bases in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G).

How many chromosomes do humans have and what are the different types called?

Humans have 46 chromosomes, which include 22 pairs of autosomes and one pair of sex chromosomes (XX or XY).

What is the role of chromosomes in humans?

Chromosomes carry genetic information and ensure proper distribution of genes during cell division.

What are alleles and their importance in the body?

Alleles are different versions of a gene that can result in varying traits; they are important for genetic diversity and inheritance.

Compare mitosis and meiosis.

Mitosis results in two identical daughter cells for growth and repair, while meiosis produces four genetically diverse gametes for reproduction.

What are the two major types of multiple births?

The two major types of multiple births are identical (monozygotic) twins and fraternal (dizygotic) twins.

Define nondisjunction.

Nondisjunction is the failure of chromosomes to separate properly during cell division, leading to an abnormal number of chromosomes in daughter cells.

What are homologous chromosomes?

Homologous chromosomes are pairs of chromosomes that have the same structure and gene sequence, one inherited from each parent.

Define genotype and phenotype with examples.

Genotype is the genetic makeup of an organism (e.g., AA, Aa, aa), while phenotype is the observable traits (e.g., tall or short plants).

How does the environment influence phenotype?

Environmental factors such as temperature, nutrition, and light can affect the expression of genes, leading to variations in phenotype.

Explain dominant and recessive traits.

Dominant traits are expressed when at least one dominant allele is present, while recessive traits are expressed only when two recessive alleles are present.

What is the difference between heterozygous and homozygous genotypes?

Heterozygous genotypes have two different alleles for a gene (e.g., Aa), while homozygous genotypes have two identical alleles (e.g., AA or aa).

What are lethal alleles?

Lethal alleles are alleles that can cause the death of an organism when present in a homozygous state.

What are mutations and how can they occur?

Mutations are changes in the DNA sequence that can occur due to errors in DNA replication, exposure to radiation, or chemicals.