What is DNA?
DNA- deoxyribonucleic acid, the hereditary material of life in a cell's nucleus |
genes- carries codes for traits |
trait- characteristic of an organism |
acquired trait- from your parents |
environmental trait- from the surrounding environment |
chromosomes contain genes which are made of DNA |
Genes are inherited from your parents. Each gene codes for 1 trait, and thousands of genes are on each chromosome. Chromosomes in humans are arranged into 23 homologous pairs |
DNA Structure
DNA is a double helix, and consists of phosphate, deoxyribose sugar, and nitrogen bases. Phosphate and sugar make the backbone, and nitrogen bases are the rungs of the ladder. |
nucleotide- a phosphate paired with a nitrogen base and deoxyribose sugar |
histone- special proteins that prevent DNA from tangling |
nucleosome- DNA and histone packages which resemble beads |
telomere- protective end on eukaryotic cells that shortens every time DNA replicates |
The 4 Nitrogen Bases
PURINES
(single-ringed) |
PYRIMIDINES
(double-ringed) |
Adenine to |
Thymine with 2 H-bonds |
Guanine to |
Cytosine with 3 H-bonds |
What Causes Genetic Diversity?
1. Crossing over in prophase I |
2. Independent assortment in metaphase I and II. The chromosomes line up randomly each time. |
Non-Disjunction
non-disjunction- a mistake that occurs during anaphase I and II, when the chromosomes do not separate and gametes end up having the wrong number |
Mitosis vs Meiosis
MITOSIS |
BOTH |
MEIOSIS |
- all daughter cells are somatic |
- both for the purpose of reproduction |
- all daughter cells are gametes |
- 2 similar cells are produced |
- both create daughter cells |
- 4 different cells are produced |
- 46 chromosomes |
|
- 23 chromosomes |
- DNA is not crossed over |
|
- DNA is crossed over |
Meiosis I and Meiosis II
MEIOSIS I |
MEIOSIS II |
Prophase I
centrioles move to opposite poles, homologous chromosomes become visible and form tetrads, crossing over occurs, genetic material is exchanged |
Prophase II
- centrioles move to opposite poles, chromosome pairs become visible, crossing over does NOT occur |
Metaphase I
- tetrads line up along the equator of the cell (staying as a pair) |
Metaphase II
- each chromosome moves to the equator of the cell |
Anaphase I
- homologous chromosomes are pulled apart creating whole paired chromosomes on each side |
Anaphase II
- each chromosome splits and moves to opposite poles, the chromatid is now considered the chromosome |
Telophase I
- nuclear membrane reforms, cytokinesis occurs, creating 2 diploid cells, which contain 46 chromosomes and are genetically different |
Telophase II
- nuclear membrane reforms, cytokinesis occurs, creating 4 haploid cells called gametes |
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Prokaryotes vs Eukaryotes
PROKARYOTES |
BOTH |
EUKARYOTES |
- no nucleus or organelles |
- both forms of life |
- nucleus and organelles |
- simple and primitive |
|
- complex cells |
- usually single-celled |
|
- can be multicellular |
Meiosis Definitions
zygote- cell created when egg and sperm unite |
karyotype- map of chromosomes organized into homologous pairs |
diploid- total # of chromosomes in an organism, somatic cells |
haploid- half the # of chromosomes in an organism, sex cells |
Purpose of Mitosis and Meiosis
MITOSIS |
MEIOSIS |
1. Asexual Reproduction
- 1 parent with identical offspring |
1. Create Gametes
- creates egg/sperm or egg/pollen
- 2 parents with genetically different offspring |
2. Repair
- to fix damaged cells and replace old cells |
3. Growth
- nuclear division, and depends
on the size and growth of the
organism |
Mutation
mutation- any change made to DNA |
4 Types of Mutations
1. Translocation |
- part of a chromosome breaks off and attaches itself to a different chromosome
- Translocation Down's |
2. Deletion |
- part of a chromosome is deleted
- Prader Willi Syndromelearning disabilities, behavioural problems, obesity, short stature, etc. |
3. Duplication |
- part of the chromosome is repeated
- cause of seizures |
4. Inversion |
- genetic code is flipped
- linked to infertility problems |
Trisomies and Traits
Trisomy 13, Patau Syndrome |
heart defects, brain and spinal cord abnormalities, extra fingers and toes, cleft lip, usu. die by 1 yr. old |
Trisomy 18, Edward Syndrome |
abnormally shaped head, clenched fists, heart defects, usu. die by 1 yr. old |
Trisomy 21, Down Syndrome |
mild disability, can still form relationships and interact in society |
Trisomy XXY, Klinefelter Syndrome |
infertile males, look childish, high pitched voice, learning disabilities |
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