chapter 13 Flashcards
asexual reproduction
a single individual passes gene to its offspring without the fusion of gametes
sexual reproduction
two parents give rise to offspring that have unique combinations of genes inherited from the two parents
Are there any organisms that can reproduce both sexually and asexually?
Yes. Ex: Aphids, flatworms, starfish
Which type of division is used for each type of reproduction?
Mitosis for asexual, meiosis for sexual
What constitutes a pair of homologous chromosomes?
homologous chromosomes, or homologs, which have the same length, shape, and carry genes controlling the same characters
If an organism’s genome consists of 2n=46, how many pairs of homologous chromosomes does it have? How many of the chromosomes are maternal in origin? How many are paternal in origin?
23 pairs of homologs; 23 maternal; 23 paternal
In humans, how many individual chromosomes and homologous pairs are autosomes? How many are sex chromosomes?
Autosomes: pairs 1-22; 44 chromosomes
Sex chromosomes: pair 23; two chromosomes
Describe the types of human sex chromosomes. Which would be present in a female? Which in a male?
The sex chromosomes, pair 23, determine the sex of the individual and are called X and Y; In an unfertilized egg (ovum), the sex chromosome is X; In a sperm cell, the sex chromosome may be X or Y. Females have XX. Males have XY
Meiosis I: Prophase I
Chromosomes begin to condense; nuclear envelope dissolves; crossing over may occur
Meiosis I: Metaphase I
homologous pairs (Tetrad) line up at the metaphase plate, with one chromosome facing each pole; Microtubules from one pole are attached to the kinetochore of one chromosome of each tetrad; Microtubules from the other pole are attached to the kinetochore of the other chromosome
Meiosis I: Anaphase I
Pairs of homologous chromosomes separate; One chromosome moves toward each pole, guided by the spindle apparatus; Sister chromatids remain attached at the centromere and move as one unit toward the pole
Meiosis I: Telophase I and Cytokinesis
chromosomes decondense; nuclear envelope reforms; each half of the cell has a haploid set of chromosomes; each chromosome still consists of two sister chromatids; Cytokinesis usually occurs simultaneously, forming two haploid daughter cells
Meiosis II: Prophase II
Chromosomes begin to condense; nuclear envelope dissolves; a spindle apparatus forms; late prophase II, chromosomes (each still composed of two chromatids) move toward the metaphase plate
Meiosis II: Metaphase II
sister chromatids align individually at the metaphase plate; The kinetochores of sister chromatids attach to microtubules extending from opposite poles
Meiosis II: Anaphase II
the sister chromatids separate and move as two newly individual chromosomes toward opposite poles
Meiosis II: Telophase II and Cytokinesis
the chromosomes arrive at opposite poles; Nuclei form, and the chromosomes begin decondensing; Cytokinesis separates the cytoplasm
How does the alignment of the chromosomes at the metaphase plate differ between meiosis 1 and meiosis 2?
Meiosis I: in homologous pair; Meiosis II: as individual, replicated chromosomes
Compare mitosis and meiosis
Mitosis conserves the number of chromosome sets, producing cells that are genetically identical to the parent cell. Mitosis conserves the number of chromosome sets, producing cells that are genetically identical to the parent cell.
Meiosis reduces the number of chromosomes sets from two (diploid) to one (haploid), producing cells that differ genetically from each other and from the parent cell. Meiosis reduces the number of chromosomes sets from two (diploid) to one (haploid), producing cells that differ genetically from each other and from the parent cell
diploid
2n, having two of each chromosome type
haploid
n, having only one of each chromosomes type
gonads
organs in animals, such as testes (male) and ovaries (female), where gametes are produced
gametogenesis
the production of gametes, such as sperm and eggs (ovum)
Gametes
Sex cells
Sperm
Male sex cell
egg (ovum)
Female sex cell
heredity
the transmission of traits from one generation to the next
variation
the differences in appearance that offspring show from parents and siblings
clone
one of a group of genetically identical individuals from the same parent
gene
the units of heredity; made up of segments of DNA found on a specific location of a certain chromosome
fertilization
fusion of gametes
locus
specific location of a gene on a chromosome
homologous chromosomes
chromosomes that have the same length, shape, and carry the same genes
somatic cell
non-gametic cells
autosomes
non-sex chromosomes
zygote
single cell that results from fertilization
