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Genetics Review and test/quiz for SBI3U
Two difference cell stages:
a.G1 Phase: Rapid Growth Cycle
b.S Phase: DNA replication
c.G2 Phase: Preparation for division (Nuclear and Cellular)
2. Cell division:
a.Mitosis: Nuclear Division
i.Prophase, Metaphase, anaphase, telophase
b.Cytokenisis: Cell division
-All Somatic cells undergo Mitotic division. This is so that the body can grow, repair, maintain, and/or replace tissues
Plant versus Animal Mitosis:
Prophase: Because plant cells do not contain centrioles, the spindle fibres form the cytoplasm which “holds” or “contains” the organelles within the cell. In animal cells, the spindle fibres come from the centrioles.
Telophase (Cytokenisis): Because plant cells have a cell wall and a cell membrane (where animal cells only have a cell membrane) a cell plate starts to form between each of the newly developing nuclei, after pinching in, in this stage. In animal cells, only pinching in would occur.
-Like mitosis, the names of each phase(s) are very similar:
-Unlike mitosis, meiosis has two divisions of the nucleus
-Only Germ Cells undergo meiosis, therefore only either a sperm or an egg cell is produced
-The purpose of Meiosis is to crease haploid cells
-After synapsis occurs, the process called Crossing over happens -The whole point of crossing over is to create genetic variation, meaning that none of the haploid cells will be similar
More Information and Significance of Gregor Mendel
There are a few different types of Inheritances:
-You will use Monohybrid crosses (involve only one characteristic ) or Dihybrid crosses (involve two characteristics ) to show the genotype(s) and the phenotype(s) of the offspring(s). See the end of this article for links on how to do these, step by step.
Mendel had three laws of genetics:
The dominant trait covers up or dominates the recessive trait.
2. Principle of Segregation:
Allele pairs separate during gamete formation and then will randomly unite during the process of fertilization.
3. Principle of Independent Assortment:
Alleles separate independently during their gamete formation so that the traits will be produced independently of one another in each offspring.
-One characteristic that has two traits
-The offspring contain two alleles (one from each parent)
To chose letters for the alleles keep in mind:
- There must only be one kind of letter, since only one characteristic is shown in the offspring
- The choice of the letter comes from the word/spelling of the dominant trait/condition
- The dominant allele is the uppercase letter and the recessive one is the lowercase letter
In height, being tall is the dominant allele and being short is the recessive one. In this case, you can only ever produce a tall or short offspring. The letter being used is T. Capital T is for a tall offspring and lower case t is for the short offspring. Show the phonetic ratio of the offspring if one parent is heterozygous tall and the other parent is homozygous short using a punnett square .
Answer To Example
The phonetic ratio of the offspring is 1:1, meaning that for every one heterozygous tall offspring there is one homozygous short offspring.
-The alleles are not always dominant over each other
-Because we now do not have a dominant allele and a recessive allele, our letter choice is going to have to change
-But because we still have to still use the same letters (since the same characteristics are being described)
Example: A red allele is incompletely dominant with a white allele so the letter choice is going to be:
RR = Red
R’R’ = White
-The R is called -prime.
-You know when alleles are incompletely dominant over each other when a new phenotype is shown in the offspring
Example: We cross a red flower with a white flower, what color would the offspring be? [RR x R’R’=?] Use a punnett square.
Punnett Square Example
The offspring is going to be a R'R. This means that the offspring will appear to be Pink.
-The word co means together
-In this case, both alleles are dominant over each other
-A new phenotype is not created this time, because both are dominant, you will see BOTH as, for example, spots
-Because we are only talking about one characteristic, we can still only use one letter
-For co-dominance, we use a base letter and a high scripted letter
-The base letter is what the alleles are affecting
-The high scripted letter is for the phenotype shown
A black feather is shown with FbFb and a white feather is shown by FwFw. A mixed offspring’s genotype would look like FwFb meaning that the offspring’s feathers would look speckled black and white.
-23 pairs of chromosomes in our body
-separated into 22 pairs of Autosomes and 1 pair of sex chromosomes
-These sex chromosome determine the sex of our offspring, XX is female and XY is male
-Sex-linked traits are on the X and Y chromosomes
-Normally simple dominance is the way to go (hence only x-linked or y-linked)
-This inheritance is the only one to break the rule for naming alleles as it has only one option
-Color blindness and haemophilia are recessive examples of recessive x-linked traits:
XH = Normal blood clotting
Xh = haemophiliac blood clotting
Y = no allele for blood clotting
-some genes have more than one allele, but it still has to be located on that one gene
-Blood typing is an example of multiple alleles – there are three:
Ia = Glycoprotein A
Ib = Glycoprotein B
I = No glycoprotein
- Ia and Ib alleles are dominant over the recessive i allele
-but, Ia and Ib alleles are co-dominant with each other
An example of crossing O blood type with A bloodtype
Blood Type Chart
- Blood Type Chart - Paternity determination by blood type - parents & child
This link is for charts that show you the outcome of crossing certain blood types with other ones. You will need to know these.
Pedigrees are another part of this unit. Following this text is a link to an explanation on how to do pedigree charts. I will explain key points that you need to know, but I would recommend that you look further into them as they are a hard to understand without many, many diagrams and face-to-face conversations and explanations.
-Pedigrees can be used to show proof of inheritance problems
-Only shows the phenotype of several generations of people. If you would like to see the genotype you will have to write them into your pedigree
-Labelling pedigrees properly is important (I, II, III generation marks on the side, a legend, etc.)
Example of a Pedigree:
Thorough Pedigree Explanation Link
- Pedigree Analysis
Here is a link to a page that explains how pedigrees work.
How to do a Monohybrid Cross
- Monohybrid Cross Problem Set
Here is a step by step instruction on how to do monohybrid crosses.
How to do a Dihybrid Cross
- Dihybrid Cross
This is a step by step instruction on how to do dihybrid crosses.
Chromatin: Material making up chromosomes, they are made up of proteins and D/RNA
Chromosomes: Found in the nucleus of cells, they carry genetic information such as genes
Sister Chromatids: 2 identical copies of chromatid attached by a centromere
Daughter Chromosomes: Produced by separation of identical sister chromatids in Anaphase in Mitosis
Spindle Fibers: Separates chromosomes into daughter cells during division
Centrioles: Develop and produce spindle fibers, near the nucleus, in an animal cell
Tetrad: Two replicated homologous chromosomes
Synapsis: The lining up of two identical tetrads, right before crossing over
Haploid: Carries only one member of each homologous pair (Ex//: Sperm or Egg)
Diploid: Carries both members of the homologous pair (Ex//: Somatic cells)
Paternal Chromosome: The chromosome received from the father (half of the gametes in you are from him)
Maternal Chromosome: The chromosome received from the mother (the other half of the gametes in you are from her)
Homologos Chromosomes: Pairs of chromosomes that are of the same length, same centromere position, same characteristics, etc. they are identical
Crossing Over: The exchange of genes between two homologous pairs resulting in the random mixture of characteristics in an offspring. This allows for genetic variation and mutations to occur.
Heterozygous: Having two different alleles of the same gene
Homozygous: Having two identical alleles of the same gene
Dominant: Alleles that are controlled by genes, and even if only one is present, will show up as characteristics in the offspring
Recessive: Alleles that are controlled by genes that only show up if they are paralleled with an identical allele. It is very common for parent(s) to have a recessive allele and not show it, only because you do need to have two of the same to show the characteristics of the allele
Punnett Square: A diagram that is used to show/predict the genetic and phonetic outcome of the offspring when two particular parents are crossed with each other
Gamete: A mature haploid cell, soon to unite with another of the opposite sex (Sperm and Eggs)
Trait: A very well perceived quality of a characteristic
Characteristic: A feature or quality that is seen
Allele: Two or more alternative forms of a gene that is found in chromosomes and arise due to random mutations
Genotype: The genetic information of an organism
Phenotype: The 'looks' of the organism that are due to the genetic information that it has, sometime as a reaction to the environment or sometime just due to random mutations that occur
I came across this when a friend told me about Khan Academy when I was having trouble with physics. He is an amazing teacher and this website is a very valuable resource. I will provide the link for the site in one second. Once you click on the link, scroll down to look for the heading biology. Click on the video title you need help with or just want to watch. Be prepared with paper and pencil in case you need to do a problem enjoy!
What to look for once on the website
Mitosis, Meiosis, and Sexual Reproduction. Khan Academy
Chromosomes, Chromatids, Chromatic, etc. Khan Academy
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Answers, Worth 1 mark each (In brackets)
1. What is the name of the genetic material during Interphase (Chromatin)
2. If a cell has 4 chromosomes and meiosis occurs, how many chromosomes will be in each of the daughter cells? (2)
3. What is the name of the genetic material during Mitosis? (Chromosomes)
4. At birth, the female eggs are at the end of this phase. (Prophase I)
5. What is the phase in which crossing over occurs? (Prophase I)
6. What is the name given to similar chromosomes? (Homologous Chromosomes)
7. In meiosis, this is the process of one replicated chromosome moving towards its similar chromosome? (Synapsis)
8. The division of the cytoplasm between the new cells after mitosis/meiosis occurs? (Cytokenisis)
9. What is the name of female meiosis? (Oogenesis)
10. What is the general name for the chromosomes from the father? (Paternal)
11. What is a pair of replicated homologous chromosomes called? (Tetrad)
Please do not depend solely on this article for studying! Use plenty of the other resources that are given to you, for example the Internet (you're already here - now try other pages too!), Libraries, and especially YOUR TEACHER. They are the most informed resource *they should be* about your class. But don't forget your Parents, they had to learn some of this too, but how much they remember. . . no one knows :)
See any issues? Please leave a comment and I will get back to you as soon as possible!
November 12, 2011.
Purchase a Textbook or Knowledge Book:
- The KEY Study Guide Biology 11 University Preparation (SBI3U)
Grade 11, University Prep Biology Notes and Problems book. I highly recommend these.
- Nelson Biology 11U - Science - Categories : Knowledge Quest Books