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Genetics Review and test/quiz for SBI3U

Updated on March 19, 2016

Mitosis


Two difference cell stages:

1. Interphase:

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.


Mitosis Cycle

Keep in mind that although this visual aid is good, the process does not stop where the arrows are shown. This cycle keeps flowing, without stop, until the cycle is done. And when triggered, will reoccur again.
Keep in mind that although this visual aid is good, the process does not stop where the arrows are shown. This cycle keeps flowing, without stop, until the cycle is done. And when triggered, will reoccur again. | Source

Mitosis Narration

Meiosis:

-Like mitosis, the names of each phase(s) are very similar:

Prophase I

Metaphase I

Anaphase I

Telophase I

Prophase II

Metaphase II

Anaphase II

Telophase II


-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

Meiosis Cycle

Here is an example of Meiosis, and keep in mind (like Mitosis) that this is a continues cycle and does not stop and then resume where arrows are shown.
Here is an example of Meiosis, and keep in mind (like Mitosis) that this is a continues cycle and does not stop and then resume where arrows are shown. | Source

Meiosis Narration

Mendelian Genetics:

There are a few different types of Inheritances:

1.Simple Dominance

2.Incomplete Dominance

3.Co-Dominance

4.Sex-Linked

5.Multiple Alleles


-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:

1. Principle of Dominance:

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.



Simple Dominance:

-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

Example:

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.

Incomplete Dominance:

-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.

Co-Dominance:

-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



Example:

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.

Example

Sex-Linked:

-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

Multiple Alleles:

-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

Here you see the offspring of this cross are only ever heterozygous A blood-type.
Here you see the offspring of this cross are only ever heterozygous A blood-type.

Pedigrees:

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:

Terminology:

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

Great Resources

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!


http://www.khanacademy.org/

What to look for once on the website

Amazing resource for almost everything!
Amazing resource for almost everything! | Source

Mitosis, Meiosis, and Sexual Reproduction. Khan Academy

Chromosomes, Chromatids, Chromatic, etc. Khan Academy

Source

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)

Source

Side note:

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.

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    • Seeker7 profile image

      Helen Murphy Howell 5 years ago from Fife, Scotland

      Excellent hub and this will be very useful for both students and anyone interested in biology. It has certainly brought home to me just how much I had forgotten. So it was great to get such a good refresher.

      Voted up!!

    • Beth100 profile image

      Beth100 5 years ago from Canada

      You've summed up the first semester in an information packed lesson. It's obvious that you've learned this and thoroughly understand the concepts. :) One suggestion: the course name is not consistent across all provinces, so I would add a general course title, such as Biology 10 or Genetics 101 or Genetics 11 or Biology 11. Other than that, EXCELLENT!! Two thumbs up! :)

      BTW, welcome! :)

    • streetdancer profile image
      Author

      Sarah H 5 years ago from Canada

      Seeker7 - thanks! I hope it it useful as I seemed to have learned more from having to type it all up! :)

    • streetdancer profile image
      Author

      Sarah H 5 years ago from Canada

      Beth100 - This isn't even the first semester! This is just one of the 5 lessons that we learned, hopefully I will be able to find enough time to post the five other ones! And maybe even a few physics one! And thanks, ill try to change the name. Cheers

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