BSC2010 - Chapter 13

Meiosis and Sexual Life Cycles

Living organisms best distinguish themselves from nonliving organisims by:

Their ability to reproduce.

Heredity

The transmission of traits from one generation to the next.

Variation

The difference in appearance that offspring show from parents and siblings.

Genetics

The scientific study of heredity and variation.

Genes

The units of heredity and are made up of segments of DNA.

Genes passed to the next generation via reproductive cells called __________.

gametes

Gametes

Sperm and eggs.

DNA is packaged into _______.

chromosomes

Somatic Cells

All the body cells in humans except the reproductive (gamete) cells.

How many chromosomes do human somatic cells have?

46 chromosomes (23 pairs, diploid).

Do somatic cells undergo mitosis or meiosis?

Mitosis – for growth, repair, and replacement of cells.

Locus

A gene’s specific position along a chromosome.

Asexual Reproduction

A single individual passes all of its genes to its offspring without the fusion of gametes.

Clone

A group of genetically identical individuals from the same parent

Sexual Reproduction

Two parents give rise to offspring that have unique combinations of genes inherited from two parents.

Life Cycle

The generation-to-generation sequence of stages in the reproductive history of an organism.

How many chromosomes do typical human somatic cells have?

23 pairs of chromosomes

Karyotype

An ordered display of the pairs of chromosomes from a cell.

What are the two chromosomes in each pair called?

Homologous chromosomes or homologs

Homologous Chromosomes

A pair of chromosomes (one from each parent) that have the same length, shape, and genes at the same locations (loci).

Homologs

Another word for homologous chromosomes — each chromosome in the pair is called a homolog.

Sex Chromosomes

Chromosomes which determine the sex (called X and Y)

What sex chromosomes do females have?

XX

What sex chromosomes do males have?

XY

What are the remaining 22 pairs of chromosomes which are not sex chromosomes called?

Autosomes

Each pair of homologous chromosomes include ______ chromosome from each parent.

one

Where does a human somatic cell get 46 chromosomes from?

One set of 23 chromosomes from the mother and another 23 from the father.

Diploid Cell

A cell that has two complete sets of chromosomes — one set from the mother and one from the father.

What is another way to express a diploid cell?

2n

In a cell in which DNA synthesis has occurred, each chromosomes is replicated:

each replicated chromosome consists of two identical sister chromatid.

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