Flashcards in Chapter 16: Inherited Change Deck (40):
How many PAIRS of matching chromosomes do humans have?
what is the definition of 'homologous'?
similar in structure and composition
what are the non-matching chromosomes in humans?
the sex chromosomes
name the two types of chromosomes
autosomes (all the other chromosomes)
each chromosome has a characteristic set of ... which code for different features
what is the locus?
the position on the chromosome where genes for particular characteristics are always found
definition of a homologous chromosome
pair of chromosomes in a diploid cell that have the same structure as each other, with the same genes at the same loci, and that pair together to form a bivalent during the first division of meiosis
definition of a gene
a length of DNA that codes for a particular protein or polypeptide
definition of an allele
a particular variety of a gene
definition of a locus
the position at which a particular gene is found on a particular chromosome; the same gene is always found a the same locus
name the two types of nuclear division
growth and sexual reproduction
what type of nuclear division is growth?
what type of division is sexual reproduction?
a cell which contains only one complete set of chromosomes
events in middle prophase 1
-homologous chromosomes pair up (synapsis)
-each pair is a bivalent
-centrosomes move to opposite ends of the nucleus
events in metaphase 1
-bivalents line up across equator of spindle, attatched by centromeres
events in late prophase 1
-nuclear envelope breaks up as in mitosis
-crossing over of chromatids may occur
events in metaphase 1
-bivalents line up across equator of the spindle, attached by centromeres
events in anaphase 1
-centromeres do not divide
-whole chromosomes move towards opposite ends of the spindle, centromeres first, pulled by microtubules
events in telophase 1
-nuclear envelope re-forms
-chromosomes reach poles of spindle
events in prophase 2
-nuclear envelope and nucleolus disperse
-centrosomes and centrioles replicate and move to opposite poles of the cell
events in metaphase 2
chromosomes line up separately across equator of spindle
events in anaphase 2
-spindle microtubules pull the chromatids to opposite poles
events in telophase 2
four haploid daughter cells are formed
the formation of male gametes
the formation of female gametes
the alleles possessed by an organism
having two identical alleles of a gene
having two different alleles of a gene
what is an 'allele?'
different varieties of the same gene
its characteristics, often resulting from an interaction between its genotype and its environment
define 'dominant allele'
one whose effect on the phenotype of a heterozygote is identical to its effect in a homozygote
define 'recessive allele'
one that is only expressed when no dominant allele is present
define 'codominant alleles'
where both alleles have an effect on the phenotype of a heterozygous organism
define 'F1 generation'
the offspring resulting from a cross between an organism with a homozygous dominant genotype, and one with a homozygous recessive genotyope
define 'F2 generation'
the offspring resulting from a cross between two F1 (heterozygous) organisms
define 'test cross'
a genetic cross in which an organism showing a characteristic caused by a dominant allele is crossed with an organism that is homozygous recessive; the phenotypes of the offspring can consequently be a guide to whether the first organism is homozygous or heterozygous
the presence of two genes that are on the same chromosome, so that they tend to be inherited together and do not assort independently
define 'gene mutation'
a change in the structure of a DNA molecule, producing a different allele of a gene