Chapter 6 Section 1 Chromosomes.
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Transcript of Chapter 6 Section 1 Chromosomes.
Chapter 6 Section 1 Chromosomes Formation of New Cells by Cell
Division
Cell division, also called cell reproduction, occurs in humans and
other organisms at different times of their life. Formation of New
Cells by Cell Division
The formation of gametes involves yet a special type of cell
division.Gametes are an organisms reproductive cells, such as sperm
and egg cells. When a cell divides, the DNA is first copied and
then distributed. Prokaryotic Cell Reproduction
Prokaryotes reproduce by a type of cell division called binary
fission. Binary fission is a form of asexual reproduction that
produces identical offspring. Prokaryotic Cell Reproduction
In asexual reproduction, a single parent passes exact copies of all
its DNA to its offspring. Binary fission occurs in two stages:
first, the DNA is copied (so that each new cell will have a copy of
the genetic information), and then the cell divides. Prokaryotic
Cell Reproduction
Eventually, the dividing cell is pinched into two independent
cells. Eukaryotic Cell Reproduction
A gene is a segment of DNA that codes for a protein or RNA
molecule. Eukaryotic Cell Reproduction
When genes are being used the DNA is stretched out, so that the
information it contains can be used to direct the synthesis of
proteins. Eukaryotic Cell Reproduction
As a eukaryotic cell prepares to divide, the DNA and the proteins
associated with the DNA coil into a structure called a chromosome.
Eukaryotic Cell Reproduction
The two exact copies of DNA that make up each chromosome are called
chromatids. The two chromatids of a chromosome are attached at a
point called a centromere. Eukaryotic Cell Reproduction
The chromatids, which become separated during cell division and
placed into each new cell, ensure that each new cell will have the
same genetic information as the original cell. How Chromosomes
Number and Structure Affect Development
Sets of Chromosomes Homologous chromosomes are chromosomes that are
similar in size, shape, and genetic content. Sets of Chromosomes
Each homologue in a pair of homologous chromosomes comes from one
of the two parents. The 46 chromosomes in human somatic cells (body
cells) are actually two sets of 23 chromosomes. Sets of Chromosomes
When a cell such as a somatic cell contains two sets of
chromosomes, it is said to be diploid. Sets of Chromosomes When a
cell, such as a gamete, contains one set of chromosomes, it is said
to be haploid. Sets of Chromosomes The fusion of two haploid
gametes a process called fertilization forms a diploid zygote. A
zygote is a fertilized egg cell. Sex Chromosome Autosomes are
chromosomes that are NOT directly involved in determining the sex
of an individual. The sex chromosomes, one of the 23 pair of
chromosomes in humans, contain genes that will determine the sex of
the individual. Sex Chromosomes In humans and many organisms, the
two sex chromosomes are referred to as the X and Y chromosomes. Sex
Chromosomes Males have an X and a Y chromosome.
Females have two X chromosomes. What do these organisms genetically
have in common? Change in Chromosome Number
Humans who are missing even 1 of the 46 chromosomes do not survive.
Humans with more than two copies of a chromosome, a condition
called trisomy, will not develop properly. Change in Chromosome
Number
Abnormalities in chromosome number can be detected by analyzing a
karyotype, a photo of the chromosomes in a dividing cell that shows
the chromosomes arranged by size. Change in Chromosome Number
Changes in an organisms chromosome structure are called mutations.
Breakage of a chromosome can lead to four types of mutations:
Deletion mutation Duplication mutation Inversion mutation
Translocation mutation