Life cycles flash card

Dogs have 78 chromosomes in their skin cells. How many chromosomes are in a dog nerve cell?
Rover is the sire of winning greyhounds. His skin cells have 78 chromosomes. How many chromosomes are in each of Rover’s sperm?
Rover and Ella are mated by a dog breeder. the resulting embryos growing in Ella’s uterus have how many chromosomes in their body cells?
Life cycles
-Stages in an organisms life from fertilization to making offspring
-generation to generation sequence of stages in the reproductive history of an organism, from conception to production of its own offspring
1n sperm and 1n egg fuse to make a 2n zygote
-1n gametes are produced
– a type of cell division that reduces a 2n set to a 1n set
-daughter cells are NOT genetically identical to parent or each other
-chromosomes are duplicated in 2n cells
The sperm in a pollen grain from a pea plant have 7 chromosomes. What is the haploid number of this pea species?
Meiosis I
-separation of homologous chromosomes during formation of gametes
-results in 2 1n cells where each chromosomes consists of sister chromatids
Prophase I
Prophase I
-chromosomes condense and homologs loosly pair along thier lengths
-Homologous chromosomes are held together by synaptonemal complex
-crossing over occurs and produces recombinant chromosomes
-each homologous pair has chiasmata
-nuclear envelope breaks down
-spindle forms and microtubules attach to kinetochores
-centrosome movement
synaptonemal complex
zipper like protein that connects homologs to each other along their lengths
crossing over
-produces recombinant chromosomes
– chunks of DNA are swapped between non sister chromatids
-a genetic rearrangement between non sister chromatids involving the exchange of corresponding segments of DNA molecules
point at which crossing over occurs, X-shaped
recombinant chromosomes
chromosomes that contain genes from both parents
Metaphase I
Metaphase I
-kinetochore of homologs are attached to microtubules from opposite poles
-pairs of homologous chromosomes are not arranged at the metaphase plate
Anaphase I
Anaphase I
Homologs seperate and move along spindle to opposite poles, guided by the spindle apparatus
-breakdown of proteins responsible for sister chromatid cohesion along chromatid arms which allows homologs to seperate
telophase I
telophase I
-(2) 1n cells
-(2) sister chromatids per chromosome
– complete haploid set of chromosomes at each pole
-cytoplasm divides
-result: (2) 1n daughter cells
-occurs simultaneously with telophase I
Meiosis II
-separation of sister chromatids during formation of gametes
– results in 4 1n cells with 1 copy of each chromosome
Prophase II
Prophase II
-new spindle forms
-microtubules attach to kinetochore
Metaphase II
Metaphase II
-chromosomes aligned in center at metaphase plate
-Kinetochore of each sister chromatid attached to microtubules from opposite poles
-if crossing over occured in meiosis I, each chromosomes are not identical
Anaphase II
Anaphase II
-proteins that hold the sister chromatids together breakdown causing chromatids to separate and move along spindle to opposite poles
Telophase II and cytokinesis
Telophase II and cytokinesis
-Nuclei form
-nuclear envelope re-forms
-chromosomes relax (decondense)
-each nucleus contains 1 copy of each chromosomes
-cytoplasm is divided
-result: 4 1n daughter cells
Genetic Variation and Meiosis
-crossing over creates recombinant chromosomes
-independent assortment randomizes which one of the homologous chromosome pairs enters a gamete
-fertilization combines chromosome sets from 2 different individuals
Independent assortment
-occurs at metaphase I
-each pair of homologous chromosomes can orient as MP or PM
– each pair of homologous chromosomes are sorted to daughter cells A or daughter cell B
-independent of every other pair of homologous chromosomes
Random Fertlization
-each egg has 1 to 2n possible chromosomes
-each sperm has 1 to 2n possible chromosomes
-2nx2n= number of possible combinations ending up in a zygote
the transmission of traits from one generation to the next
Scientific study of heredity and hereditary variations
parents endow their offspring with coded information in the form of heredity units
a gene’s specific location along the length of a chromosome
asexual reproduction
a single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes
the resulting ordered display of pairs of ordered chromosomes
homologous chromosomes
two chromosomes of a pair have the same length, centromere position, and staining pattern
sex chromosomes
X and Y chromosomes, determine a person’s sex
diploid cell
any cell with 2 chromosomes (2n) (somatic cells)
haploid cell
any cell with a single set of chromosomes (1n) (gametes)
union of gametes culminating in fusion of their nuclei
resulting fertilized egg
DNA replication: occurs during interphase before this beings
DNA replication: occurs during interphase before this beings
Number of divisions: one, including prophase, prometaphase, metaphase, anaphase, and telophase
number of divisions: two, each including prophase, metaphase, anaphase, and telophase
Synapsis of homologous chromosomes: does not occur
synapsis of homologous chromosomes: occurs during prophase I along with crossing over between non sister chromatids, resulting chiasmata holds pair together due to sister chromatid cohesion
# of daughter cells and genetic composition: two, each diploid and genetically identical to the parent
# of daughter cells and genetic composition: four, each haploid, containing half as many chromosomes as the parent, genetically different than the parents and from each other
synapsis and crossing over
During prophase I, duplicated homologs pair up, and the formation of the synaptonemal complex between them holds them in synapsis. crossing over also occurs during prophase I. both normally do not occur during prophase of mitosis
homologous pairs at the metaphase plate
at metaphase I of meiosis, chromosomes are positioned at the metaphase plate as pairs of homologs, rather than individual chromsomes, as in metaphase of mitosis
Seperation of homologs
at anaphase I of meiosis, the duplicated chromosomes of each homologous pair move toward opposite poles, but the sister chromatids of each duplicated chromosome remain attached. in contrast, in mitosis the sister chromatids seperate
parents pass genes to their offspring, the genes program cells to make specific enzymes and other proteins, whose cumulative action produces an individual’s inherited traits
Explain what causes the traits of parents (such as hair color) to show up in their offspring
In figure 10,4, how many DNA molecules (double helices) are present?
Each sperm of a pea plant contains seven chromosomes. what are the haploid and diploid numbers for this species?
Similar= each have two sister chromatids
-positioned on metaphase plate
Different= mitosis-sister chromatids are genetically identical, can be either a diploid or haploid set
-meiosis- sister chromatids are not identical due to crossing over, always a haploid set
How are the chromosomes in a cell at metaphase of mitosis similar to and different from the chromosomes in a cell at metaphase of meiosis II?
What is the original source of variation among the different alleles of a gene?
homologous chromosomes move toward opposite poles of a dividing cell during
a) mitosis
b) meiosis I
c) meiosis II
d) fertilization
e) binary fission
If the DNA content of a diploid cell in the G1 phase of the cell cycle is X, then the DNA content of the same cell at metaphase in meiosis I would be
a) 0.25x
b) 0.5x
c) x
e) 4x
If the DNA content of a diploid cell in the G1 phase pf the cell cycle is X, then the DNA content of a single cell at metaphase of meiosis II would be
a) 0.25x
b) 0.5x
c) x
e) 4x

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