Exam 4 part 5 Flashcards
What cell cycle checkpoint most frequently fails in cancerous cells
G1
How do malignant cells travel through the body
Lymphatic and circulatory systems
What protein actually triggers the production of S-phase proteins
E2F
What are the components of an organism’s karyotype
Number of chromosomes the type of chromosomes that a particular organism has
What is the relationship between homologous chromosomes and alleles
Alleles are gene that are encoding same trait, homologous is one from mom one from dad
What does the term “ploidy” mean
How many copies of chromosomes
Describe the main difference between Meiosis I and Meiosis II
In Meiosis I, homologs split
In meiosis II, sister chromatids separate
What splits when homologs split during Meiosis 1
Synaptonemal complex
When sister chromatids separate in Meiosis II, what is splitting apart
cohesions
What is forming when you see the Chiasma? What is occurring here
Tetrad (or bivalent)
Crossing over occurs
Why are you haploid at the end of Meiosis I
Because Meiosis I is when you are doing the reductive division; goes from diploid to haploid
Daughter cells now only have 1 copy of each homologous chromosome
Why are you still haploid at the end of Meiosis II
Because all you did in Meiosis II is break apart the sister chromatids
What is produced through asexual reproduction
clones
What causes genetic variation in sexual reproduction?
Independent assortment, crossing over and outcrossing
Independent assortment
you never know what side of Metaphase plate the homologous chromosomes will end up on. Separation and distribution of homologous chromosomes during Meiosis I can result in a variety of combinations of maternal and paternal chromosomes
Crossing over
new combinations of alleles on the same chromosomes; combinations that did not exist in each parent
Outcrossing
during fertilization; gametes from two different individuals combine to form offspring
How is it possible for an organism that self-fertilizes itself to produce offspring that are genetically different
Still 2 copies of each chromosome so they can line up differently and be split up differently
So they can still do crossing over and independent assortment
If homologs or sister chromatids don’t separate completely, what is this mistake called
Nondisjunction
What does nondisjunction result in
Aneuploid zygotes which means too few or too many chromosomes. typically dont survive to produce viable offspring
How common is nondisjuction
happens in as many as 10 percent of meiotic divisions
what is down syndrome an example of
trisomy
Down’s syndrome occurs due to nondisjunction during Meiosis I, a result in the failure in the breakdown of what
Synaptonemal complex
Why would males be considered a disadvantage of sexual reproduction
Males do not directly reproduce
What is the Purifying Selective Hypothesis
Anything that compromises your fitness is removed through the process of purifying selection
Natural selection against deleterious alleles
What is the Changing-Environment hypothesis
Offspring that are produced by sexual reproduction are more likely to survive and produce offspring if the environment changes
Sexually produced offspring can evolve quicker
What plant did he use for his experiments
common garden peas
Describe blending inheritance vs. inheritance of acquired characteristics
Blending: parental traits blend such that their offspring have intermediate traits
Acquired characteristics: parental traits are modified then passed on to their offspring
What characteristics do model systems usually have
Easy to grow Reproductive cycle is short Produces large numbers of seeds Matings are easy to control Traits are easily recognizable
How did Mendel arrange matings
Mendel prevented self-fertilization by removing male reproductive organs
Then he used pollen from other plants to fertilize these flowers thereby performing cross-fertilization
What traits did Mendel look at in the peas
Seed shape Seed color Pod shape Flower color Flower and pod position Stem length
