better chapter 10 flashcards

What is heredity?

The passing of traits from parents to offspring.

What is variation?

Differences in characteristics among individuals of the same species.

What is genetics?

The scientific study of heredity and variation.

What is a gene?

A segment of DNA containing information for a functional product that can influence traits.

What is a gamete?

A haploid reproductive cell, such as a sperm or egg.

What is a somatic cell?

A body cell that is not a reproductive cell.

What is a locus?

The specific location of a gene on a chromosome.

How does asexual reproduction work?

One parent produces offspring without gamete fusion. Offspring are usually genetically identical, except for mutations.

How does sexual reproduction work?

Gametes fuse during fertilization, combining parental genetic material to produce genetically unique offspring.

What is a karyotype?

An organized display of an individual's chromosomes arranged into pairs.

Why are chromosomes photographed during metaphase for a karyotype?

They are condensed and visible, making them easier to examine and arrange.

How are chromosomes arranged in a karyotype?

By size, shape, centromere position, and banding patterns.

What are homologous chromosomes?

A pair with the same genes at the same loci, one inherited from each parent. They may carry different alleles.

What are sex chromosomes?

Chromosomes involved in biological sex determination; humans typically have XX or XY.

What are autosomes?

Chromosomes other than sex chromosomes. Humans typically have 22 pairs.

What does haploid (n) mean?

One set of chromosomes. Human sperm and eggs each contain 23 chromosomes.

What does diploid (2n) mean?

Two sets of chromosomes. Most human body cells contain 46 chromosomes.

How does fertilization restore diploidy?

Two haploid gametes fuse, forming a diploid zygote with 46 chromosomes in humans.

What separates in meiosis I?

Homologous chromosomes separate; sister chromatids remain attached. Chromosome sets are reduced by half.

What separates in meiosis II?

Sister chromatids separate, similarly to mitosis.

How many DNA replications and divisions occur in meiosis?

DNA replicates once, followed by two cell divisions.

What is synapsis, and when does it occur?

Homologous chromosomes pair closely during prophase I.

What is a tetrad?

Two paired homologous chromosomes containing four chromatids total.

What is crossing over?

Nonsister chromatids of homologous chromosomes exchange corresponding DNA segments during prophase I.

What are chiasmata?

Visible points where homologous nonsister chromatids remain connected after crossing over.

How does crossing over create variation?

It produces recombinant chromosomes with new combinations of alleles.

What is independent assortment?

Homologous chromosome pairs orient independently during metaphase I.

How does independent assortment create variation?

It distributes different combinations of maternal and paternal chromosomes into gametes.

How many chromosome combinations can human gametes have from independent assortment alone?

2^23, or about 8.4 million combinations per gamete.

What is the main function of mitosis?

Growth, tissue repair, and cell replacement while usually maintaining chromosome number.

What is the main function of meiosis?

Producing haploid cells for sexual reproduction and generating genetic variation.

How many daughter cells does mitosis usually produce?

Two daughter cells.

How many daughter cells does meiosis typically produce?

Four haploid cells.

How does chromosome number differ in mitosis and meiosis?

Mitosis usually maintains chromosome number; meiosis reduces it by half.

How do daughter cells differ after mitosis and meiosis?

Mitosis usually produces genetically similar cells. Meiosis produces genetically different haploid cells.

Do homologous chromosomes pair in mitosis?

No. Homologous chromosomes pair as tetrads during prophase I of meiosis.

Which process normally includes crossing over: mitosis or meiosis?

Meiosis, during prophase I. Crossing over is not a normal feature of mitosis.

What separates first in mitosis versus meiosis?

Mitosis separates sister chromatids. Meiosis I separates homologous chromosomes.

What do mitosis and meiosis have in common?

Both follow DNA replication and use spindle fibers to move chromosomes through division stages.

What are the two major sources of variation during meiosis?

Crossing over during prophase I and independent assortment during metaphase I.

How does random fertilization increase variation?

Any genetically unique sperm may fuse with any genetically unique egg.

How many chromosome combinations can fertilization produce in humans from independent assortment alone?

About 2^23 × 2^23 = 2^46, or roughly 70 trillion combinations.

Why is the 70-trillion estimate incomplete?

It excludes the additional variation produced by crossing over.

Why is genetic variation important for evolution?

It gives natural selection inherited differences to act on.

How can a beneficial allele become more common?

If it improves reproductive success, carriers may leave more offspring, increasing its frequency over generations.

What could happen to a population with little genetic variation?

It has fewer inherited differences that natural selection can act on when the environment changes.