Download Unit 3- study guide Test 1

Genetics - Test A - Study Guide
Sexual vs. Asexual
1. What is/are the difference(s) between sexual and asexual reproduction? Asexual—makes clones, identical,
diploid (full set of chromosomes), fast, easier form of reproduction, takes less energy
Sexual—makes genetically different organisms, diploidhaploid (half set of chromosomes), takes more time,
takes more energy, and most importantly it increases genetic diversity
2. What does sexual reproduction help to create and maintain? How does this help a species if its environment
changes for some reason? GENETIC DIVERISTY; this increases the chances that when an environment changes at
least some of the organisms will be “best adapted” to this new environment and thus be able to survive and
reproduce keeping the species alive
3. Are the offspring from asexually reproducing organisms genetically similar or different from their parent? Is this
a good or bad trait? Explain your answer. Asexual reproduction produces clones, exact copies of the parent cell.
It’s generally bad because all the species have the same exact traits. If the environment negatively changes, all
the species will die out because everyone is the same.
4. What is alternation of generations? How does this process relate to sexual and asexual reproduction?
Alternation of generations is a cycle where organisms alternate between mitosis and meiosis, asexual and sexual
reproduction respectively.
5. Fill in the following chart:
FORM OF ASEXUAL
REPRODUCTION
BINARY FISSION
BUDDING
DESCRIPTION
Bi=2, fission=split,
Asexual reproduction where the cell splits into 2, both are identical
Budding is a form of asexual reproduction in which a new organism
develops from an outgrowth or bud on another one due to cell division
at one particular site. The new organism remains attached as it grows,
separating from the parent organism only when it is mature, leaving
behind scar tissue.
Cloning is two identical organisms created from a single cell
CLONING
SPORE FORMATION
VEGETATIVE
PROPAGATION
A spore is a unit of asexual reproduction that may be adapted for
dispersal and for survival, often for extended periods of time, in
unfavorable conditions. A spore is a haploid cell that can form a new
organism on its own.
Vegetative Propagation is a form of asexual reproduction in plants. It
is a process by which new organisms arise without production of
seeds or spores. A new plant is produced from a plant’s own stems
and roots.
6. Label each of the following as an advantage of sexual reproduction (S) or asexual reproduction (A):
___A__ Benefits isolated or simple organisms ___S__ Provides genetic diversity
___A__ Requires less energy
___A_ Rapid reproduction
___S__ Provides disease resistance
___S_ Increases adaptation
Mitosis vs. Meiosis
7. What are the four (4) phases of mitosis (in order)? PMAT, Prophase, Metaphase, Anaphase, Telophase
8. What is the relationship between chromatin and chromosomes and chromatids? Chromatin is a condensed
form of a chromosome, chromosomes are the full uncondensed form, and chromatids are one half of a chromosome
9. In which phase of Mitosis are the chromatids pulled apart? Which phase of Meiosis? Anaphase, Anaphase II
10. In which phase of Mitosis does the nuclear membrane DISSAPPEAR and then REDEVELOP? In Meiosis?
Disappears—Prophase (Mitosis), Prophase I (Meiosis), Reappears—Telophase I (Mitosis), Telophase II (Meiosis)
11.
Why is it important that DNA is replicated before division? During which phase of the cell cycle is DNA
duplicated? So that each cell receives a full copy of DNA, S Phase of Interphase
12.
You are looking at a cell under the microscope. You notice that the chromosomes are lined up in pairs
in the middle of the cell. This would tell you that the cell is in which phase of cell division? Metaphase
(Meta=Middle)
13.
How are mitosis and cancer related? Cancer is uncontrolled mitosis (the cells will NOT stop dividing)
14. Why do humans need Mitosis? Why do humans need Meiosis? Mitosis is important for cell growth and repair
of pre-existing cells, whereas Meiosis is only for sexual reproduction (sperm and egg)
15. What is the difference between n and 2n ? N= Haploid (half set of chromosomes) and 2N= Diploid (full set
of chromsomes)
16. What are homologous chromosomes? Which parent donates homologous chromosomes? Homologous
chromosomes are chromosome pairs, one from each parent, that are similar in length, gene position and
centromere location; both parents donate homologous chromosomes (1/2 from each)
17. What do the terms diploid and haploid mean? Haploid (half set of chromosomes) Diploid (full set of chromsomes)
In humans, our diploid number is 46 and our haploid number is 23
18. Why is crossing over important? When does it happen? Crossing over is where the paternal and maternal
chromsomes “cross over” each other and exchange genetic information to create a new chromosome, with some of
both parent’s DNA. This occurs in Prophase I.
19. Why is meiosis important for the formation of gametes, or what would happen if meiosis didn’t occur in
gametes? We would be a clone of one of our parents.
20. What is a polar body? There are 4 haploid cells produced at the end of Meiosis, but only one egg and sperm cell are
needed, so the other 3 disintegrate and they are known as “polar bodies”
21. The following phases are not in order. Match each description to the correct picture:
PHASES of MITOSIS
___13__ A. Stage of meiosis where crossing over occurs.
___8_ B. Metaphase I
___1__ C. Anaphase
___5__ D. Metaphase
___7__ E. Anaphase II
___12_ F. Telophase II
___2__ G. Prophase
22. Fill in the following chart
PHASE
INTERPHASE
SKETCH
SUMMARY
G1= GROW
S = SYNTHESIS (DNA
COPIED)
G2= GROW
Chromosomes become more
coiled and can be viewed
under a light microscope.
PROPHASE
• Each duplicated
chromosome is seen as a pair
of sister chromatids joined by
the duplicated but
unseparated centromere.
• The nucleolus disappears
during prophase.
• In the cytoplasm, the
mitotic spindle, consisting of
microtubules and other
proteins, forms between the
two pairs of centrioles as they
migrate to opposite poles of
the cell.
• The nuclear envelope
disappears at the end of
prophase. This signals the
beginning of the substage
called prometaphase.
• The centrosomes are at
opposite poles of the cell.
• The chromosomes, now at
their most highly coiled and
condensed, become arranged
on a plane equidistant from
the two poles called the
metaphase plate.
METAPHASE
• For each chromosome, the
kinetochores of the sister
chromatids face the opposite
poles, and each is attached to
a kinetochore microtubule
coming from that pole.
• Anaphase begins when the
duplicated centromeres of
each pair of sister chromatids
separate, and the nowdaughter chromosomes begin
moving toward opposite poles
of the cell due to the action of
the spindle.
• Depending where the
centromere is located along
the chromosome, a
characteristic shape appears
during chromosome
movement. The two shown
above give V and J shapes.
ANAPHASE
SEE PICTURE IN CYTOKINESIS
TELOPHASE
• At the end of anaphase, a
complete set of chromosomes
has assembled at each pole of
the cell.
• The chromosomes assemble
in sets at the two poles.
• The chromosomes begin to
uncoil and eventually assume
the extended state
characteristic of interphase.
• A nuclear envelope reforms
around each chromosome set,
the spindle disappears, and
the nucleolus reforms.
Nuclear division by mitosis is
complete at this point.
• Cytokinesis, the division of
the cytoplasm, usually is in
progress before nuclear
division is complete. In
animal cells, cytokinesis
involves the formation of a
cleavage furrow resulting in
the pinching of the cell into
two.
CYTOKINESIS
23. Fill in the following chart:
POINT OF COMPARISON
MITOSIS
HOW CHROMOSOMES ALIGN
IN METAPHASE
Chromosomes align in the
middle
# OF CHROMOSOMES AT THE
END OF THE PROCESS
Diploid
Haploid
# OF DAUGHTER CELLS
FORMED FROM ONE (1)
PARENT CELL
2
4
WHERE THE PROCESS TAKES
PLACE (WHAT TYPE OF CELL?)
Prokaryotes and Eukaryotes
Eukaryotes Mainly (few
exceptions)
# OF PHASES
4
MEIOSIS
Metaphase I—Homologous
chromosomes align in the
middle
Metaphase II-Sister
chromatids align in the
middle
8
Genetics
24. “The Father of Genetics” = ________Gregor Mendel________________
25. In your own words, explain his 3 principles/Laws:
a. Independent Assortment - states that allele pairs separate independently during the formation of gametes.
This means that traits are transmitted to offspring independently of one another.
b. Dominant & Recessive traits – dominant traits mask the recessive traits
c. Segregation of factors -
states that allele pairs separate or segregate during gamete formation, and
randomly unite at fertilization.
26. Humans have _46___ (2n) chromosomes in each ____body cell_____(somatic) cell.
27. Humans have _23___ (1n) chromosomes in each _____germ cell____ (sex cell).
28. ___Traits____________ – different forms of the same gene (flower color)
29. _____Crossing Over_______________ ______________ occurs when chromatids
of homologous pairs become entangled. This happens during the phase called
_Prophase I__________________. (It is the Homologous pair that is pulled apart during Anaphase I)
30. _Honozygous_____- when the traits/genes (alleles for the trait) are represented
by letters (Tt, Aa, BB, dd)
31. Genotypic ratios are written in the following order: _____Homozygous Dominant_________ :
_____Heterozygous_________: _____Homozygous Recessive_________
32. ____Phenotype______________– the physical appearance or what the offspring looks like.
(Tall : short, curly hair : straight hair)
Phenotype ratios are reported from the Dominant to the Recessive trait showing.
The physical appearance of
The physical appearance of
Homozygous Dominant & Heterozygous : Homozygous Recessive
33. __ Homozygous Dominant ________________- both capital letters/dominant for genotype (TT , AA, BB)
34.____ Heterozygous _________________ - One letter is capital/dominant & one is small/recessive (Tt, Aa, Bb)
35. ___ Homozygous Recessive ______________________ – both letters are small/recessive (tt, aa, bb)
36. ____Punnett Square__________________– diagram showing probability of traits
Parental alleles – from the gametes (genotype) go on the outside of the box
37. Dominant___________ (capital letter) trait will always show if present (covers any recessive traits)
38. Recessive___________ (lower case letters) – trait is masked or covered by the dominant.
Recessive traits only show up if homozygous recessive (lower case letters)
39. Solve the Punnett square below:
T
t
T
t
TT
Tt
Tt
tt
40. Complete the ratios below based on the Punnett square in #39.
1 :
2 :
HD: He : hr
1 Genotypic ratio
3
:
1
Phenotypic ratio
show trait : don’t show trait
DON’T FORGET TO LOOK AT
EVERYTHING IN YOUR LOGBOOK! GO
OVER INCOMPLETE AND
CODOMINANCE PUNNETS AND
PEDIGREES!