Alternate assignment for exam 3 Flashcards
Somatic cell
A typical body cell within an organism
Germ cell
A cell containing half the number of chromosomes of a somatic cell and able to unite with one from the opposite sex to form a new individual; a gamete
Autosomal chromosome
control the inheritance of all an organism’s characteristics except the sex-linked ones
Sex chromosome
Sex chromosomes (X,Y) contain the genetic information that instructs the developing offspring to become one sex or the other
Meiosis
The type of cell division that produces haploid gametes from diploid parent cells
Gene locus on a chromosome
The location of a gene on a chromosome
Why do diploid cells ALWAYS have an even number of chromosomes?
Becausechromosomes comein pairs
Zygote
A diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum
Sex determination system
A biological system that determines the development of sexual characteristics in an organism
What type of cell division produces sperms and eggs (gametes)?
meiosis
What kind of cell division occurs so that zygote develops into a multicellular fetus?
mitosis
Prophase I (meiosis 1)
the chromatin coils up into the chromosomes. In a process called synapsis the homologous chromosomes, each with their sister chromatids come together as pairs. The resulting structure is called a tetrad
Metaphase I (meiosis 1)
tetrads align on the metaphase plate. Spindle microtubules are attached to the kinetochores at the centromeres. Crossing over between homologous chromosomes comes to an end. NOTE: spindle microtubules attached to one homologous chromosome are from one pole of the cell, and the other homologous chromosome is attached to microtubules from the other pole.
Anaphase I (meiosis 1)
homologous chromosomes are pulled away from one another to opposite polls. Each chromosome is in the form of two sister chromatids attached at the centromere. At the end of anaphase there is a haploid number of chromosomes approaching the two poles of the cell.
Telophase I (meiosis 1)
the chromosomes arrive at the poles, cytokinesis occurs and two haploid daughter cells are formed.
Independent assortment of chromosomes
Homologous chromosomes, or tetrads, line up randomly during metaphase I on the metaphase plate before being separated during anaphase I. The total number of combinations of chromosomes that meiosis can package into gametes because of this randomization is 2n , where n is the haploid number of the organism in question
Prophase II (meiosis 2)
spindle forms and moves chromosomes toward middle of cell
Metaphase II (meiosis 2)
chromosomes aligned on metaphase plate. This time the kinetochores of the sister chromatids face opposite poles with the spindle microtubules attached from the corresponding poles.
Anaphase II (meiosis 2)
centromeres of sister chromatids finally separate and each chromatid moves to opposite poles
Telophase II (meiosis 2)
nuclei form around the haploid collection of chromosomes
What are the three sources of genetic variability in the offspring of sexually reproducing organisms?
- Crossing over during prophase I
- Independent assortment of homologous chromosomes at metaphase I
- Ultimately random fertilization creating the zygote
What are the sex chromosomes in humans?
In humans the X and Y chromosomes are the sex chromosomes and the combination of these chromosomes determines the sex of the organism.
What are the sex chromosomes in humans? What combination of sex chromosomes produces a female?
In humans, the somatic cells in females have a XX set
In humans, the somatic cells in males have a XY set
In humans the father’s sperm always determines the sex of the offspring
What are the sex chromosomes in birds? What combination of sex chromosomes
produces a female bird? What combination produces a male bird? So, is it the hen or the rooster that determines the sex of their offspring?
the egg cell (mother) determines the sex of the offspring. Female birds contain one of each of the sex chromosomes (Z, W). Male birds have two of the Z chromosomes (Z, Z)
