Chromosomes
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Chromosomes Chapter 6.1
What is a Chromosome?
Chromosome – a structure made of DNA and associated proteins on which genes are located.
DNA and proteins are “coiled up” in chromosomes.
Genes are segments of DNA that code for proteins or RNA molecules.
Play an important role in how a person’s body develops and functions.
Chromosomes are made of 2 Chromatids. Two chromatids of a chromosome are attached at a point called a centromere.
Why are Chromosomes split into Chromatids during Cell Division?
To ensure that each cell has the same genetic information. How may chromosomes do humans have?
23 pairs of chromosomes (46 total) One set from the mother and one set from the father
Cells with two sets of chromosomes are called diploid. (Somatic Cells) Cells with one set of chromosomes are called haploid. (Gametes – Sex Cells) During fertilization, two haploid cells merge to form a diploid cell (Zygote).
Our chromosomes are homologous
(similar in size, shape, and genetic content)
22 pairs of our chromosomes are called Autosomes. The other pair are called the sex chromosomes.
Males
XY chromosomes
Females
XX chromosomes
** Sex is determined by the male, since the male can donate both an X and Y chromosome.
Karyotypes are used to examine an individual’s chromosomes.
Abnormal numbers of chromosomes can cause problems: Having too few chromosomes results in death. Having too many can cause abnormalities
Ex. Down Syndrome
Down Syndrome (Trisomy 21) is caused by a diploid gamete fusing with a haploid gamete during fertilization.
3 copies of chromosome 21.
Mutations
Deletion – piece of chromosome breaks off completely Duplication – fragment attaches to its homologous chromosome Inversion – fragment reattaches on the opposite side. Translocation – fragment attaches to a nonhomologous chromosome.
What is a Chromosome?
Chromosome – a structure made of DNA and associated proteins on which genes are located.
DNA and proteins are “coiled up” in chromosomes.
Genes are segments of DNA that code for proteins or RNA molecules.
Play an important role in how a person’s body develops and functions.
Chromosomes are made of 2 Chromatids. Two chromatids of a chromosome are attached at a point called a centromere.
Why are Chromosomes split into Chromatids during Cell Division?
To ensure that each cell has the same genetic information. How may chromosomes do humans have?
23 pairs of chromosomes (46 total) One set from the mother and one set from the father
Cells with two sets of chromosomes are called diploid. (Somatic Cells) Cells with one set of chromosomes are called haploid. (Gametes – Sex Cells) During fertilization, two haploid cells merge to form a diploid cell (Zygote).
Our chromosomes are homologous
(similar in size, shape, and genetic content)
22 pairs of our chromosomes are called Autosomes. The other pair are called the sex chromosomes.
Males
XY chromosomes
Females
XX chromosomes
** Sex is determined by the male, since the male can donate both an X and Y chromosome.
Karyotypes are used to examine an individual’s chromosomes.
Abnormal numbers of chromosomes can cause problems: Having too few chromosomes results in death. Having too many can cause abnormalities
Ex. Down Syndrome
Down Syndrome (Trisomy 21) is caused by a diploid gamete fusing with a haploid gamete during fertilization.
3 copies of chromosome 21.
Mutations
Deletion – piece of chromosome breaks off completely Duplication – fragment attaches to its homologous chromosome Inversion – fragment reattaches on the opposite side. Translocation – fragment attaches to a nonhomologous chromosome.
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