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Genetics
the scientific study of heredity and variation
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Heredity
- the transmission of traits from one generation to the next
- Offspring inherit genes, not traits
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Variation
- by the differences in appearance that offspring show from parents and siblings
- lead by sexual reproduction
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genes
- units of heredity
- Each gene = specific location on a chromosome ( a locus)
- Version of a gene = an allele
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gametes
- reproductive cells, the vehicles that transmit genes from one generation to the next
- - contain haploid cells
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somatic cells
- all cells of the body except the gametes and their precursors
- contains 46 chromosomes in humans (23 pairs)
- maternal set (from our mother) and a paternal set (from our father)
- 1 chomosome contains several hundreds to thousands of genes in sequences of nucleotides
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locus
gene’s specific location along the length of a chromosome
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asexual reproduction
- a single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes.
- give rises to a clone(a group of genetically identical individuals)
- Ex: mitotic cell division
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sexual reproduction
two parents give rise to offspring that have unique combinations of genes inherited from the two parents
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karyotype
chromosomes are arranged in pairs, starting with the longest chromosomes
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homologous chromosomes
- pair of two chromosomes (represent by n)
- Same length, same centromere position, carry versions of the same genes, govern the same traits
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sex chromosomes
- the Xand Y chromosomes
- Female has pair of (XX) Male has pair of (XY)
- autosomes - other chromosomes
- unfertilized egg = X
- sperm = X or Y
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diploid cell
- cell with two chromosome sets (2n)
- human = 46 (2n = 46)
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haploid cells
- number of chromosomes (n).
- For humans, the haploid number is 23 (n = 23)
- consists of the 22 autosomes plus a single sex chromosome
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