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Heredity
Basic, Beyond Basic and Lab Terms
Term | Definition |
---|---|
allele | one of two or more forms of a gene (ex:W or w for widow's peak trait) [B] |
fertilization | the joining of a haploid egg cell and a haploid (1n) sperm cell to form a diploid (2n) zygote [B] |
meiosis | followed by cytokinesis, this double division of the nucleus produces four unique haploid (1n) egg or sperm cells (only 1 egg cell is viable) [B] |
dominant and recessive alleles | 1) expressed if at least one allele is present 2) only expressed when a dominant allele is not present [B] |
sex chromosome | in humans, these chromosomes are X and Y. XX produces females and XY produces males [B] |
sex-linked traits | typically found on X chromosomes (ex:color blindness), to express the trait, men need one copy of the gene (ex:XcY) and females need two copies (ex:XcXc) [B] |
homozygous and heterozygous | 1) a genotype with two identical alleles (ex: WW or ww) 2) a genotype with two different alleles (ex:Ww) [B] |
gene | a section of DNA in a chromosome that codes for a protein (or polypeptide) [B] |
gamete | egg or sperm cells (haploid/1n) [B] |
genome | The complete complement of an organism's genes; an organism's genetic material [BB] |
sexual reproduction and genetic variation | variation is increased by reproduction with two parents by (1) crossing-over during meiosis, (2) random assortment of chromosomes during meiosis, and (3) many possible combinations of gametes during fertilization [BB] |
polyploidy | primarily in plants, this is the case in which an organism has one or more duplicate sets of chromosomes, 3 sets (3n) can result in sterility (seedless watermelons) and 4 sets (4n) can result in enlarged fruit (strawberries) [BB] |
monosomy and trisomy | 1) one missing chromosome or 2) one extra chromosomes as a result of nondisjunction often result in human disorders including Trisomy 21 (Down syndrome) and XO (Turner syndrome) [BB] |
rules of probability | addition rule: or = + multiplication rule: and = X [BB] |
multiple gene | many traits are the product of more than one gene [BB] |
nonnuclear inheritance | chloroplast and mitochondrial DNA (not found in the nucleus) are randomly assorted to gametes and do not follow simple Mendelian rules -- mitochondria is transmitted by the egg in animals [BB] |
segregation (chromosomal) | Mendel's first law, stating that allele pairs separate during gamete formation, and then randomly re-form pairs during the fusion of gametes at fertilization [BB] |
independent assortment | Mendel's second law, stating that each allele pair segregates independently during gamete formation [BB] |
nondisjunction | An accident of meiosis or mitosis, in which both members of a pair of homologous chromosomes or both sister chromatids fail to move apart properly (can result in monosomy or trisomy) [BB] |
homologous chromosomes | chromosome pairs of the same length, one inherited from each parent (each duplicated form is made up of two sister chromatids) [Lab: Mitosis/Meiosis] |
crossing-over | the exchange of genetic material between nonsister chromatids during synapsis (pairing of homologous chromosomes) of prophase I of meiosis [Lab: Mitosis/Meiosis] |