SBI3U Grade 11 Biology Genetics Test Review Questions

Unit 2: Genetic Processes Review

 

DNA

  1. DNA is important to the human body because it provides the instructions for life. It is an instruction maual that builds and contains all the information in our bodies. Without it, everyone would look the same and so, it is responsible for making individuals.
  2. DNA is a biolgical moelcule called a nucleic acid. 3 smaller molecules make up DNA which include Deoxyribose sugar, Phosphate and the Nitrogenous bases of Adenine, Thymine, Cytosine and Guanine. It contains all the information of life and is shaped like hexagons.
  3. Base pairing is the rungs that are made up of 2 of the nitrogeneous bases bonded together, which follow the pattern of A always bonding with T and C always bonding with G. A stands for Adenine, T stands for Thymine, C stands for Cytosine, and G stands for Guanine.
  4. A nucleotide is made up of 3 parts, 1 sugar, 1 phosphate and 1 nitrogeneous base. These can beany nitrogeneous base along with sugar deoxyribose and any phosphate group.
  5. The Human genome project has allowed the development of genetic tests to screen for genetic diseases. We can see DNA mutations in genes and therefore identify problems, which is huge in creating the future medicine and cures for human dieases and mutations.

Cell Division

  1. Somatic cells are body cells while gametes are sex cells. Gametes are found only in reproductive organs and each have 23 chromosomes. Somatic cells have 46 chromosomes and are found anywhere in the body other then in the sex cells.
  2. Gametes are the egg and sperm cells in our body, each consisting of 23, a haploid number. In order for reporduciton to take place, the gametes must come together, so when the haploid sperm and the haploid egg are fused, they fuse to get a diploid number, which is a fertilized zygote. This also ensures variation and that the daughter cells do not receive two complete sets of chromosomes. Insetead, the daughter cells should grow through mitossi to beomce diploid. Somatic cells are diplod because they have 2 sets off 23 chromosomes. Each daughter cell gets two complete sets of chromosomes and this produces 2 cells that are identical to the mother cell.
  3. The cell cycle has 2 main stages, growth and division. The growth stage is called interphase and the division stage is both Mitosis and Cytokinesis. In Interphase, the G1 phase is responsible for growth and preparation. The S phase is next, and it allows for DNA synthesis(copying DNA). Lastly, the G2 phase is responsible for the preparation for division. Next comes mitosis, where it is Prophase, Metaphase, Anaphase and Telophase. Prophase is when the chromatin coil up to form chromosomes. The spindle fibres begin to form and the nucleur membrane vanishes. Lastly, the centrioles migrate to opposite poles. In Metaphase, the spindle fibres attach to the chromsomes and allign on the equatorial plate(middle). The sister chromatids face opposite poles. In Anaphase, the centromere on the chromosome splits and the sister chromtids are pulled to opposite poles by the spindle fibres. Finally, in Telophase, the nuclear membrane forms around the chromatids and the spindle fibres disappear and the chromatids decondense to chromatin. In Cytokinesis, the cytoplasm divides and forms 2 daughter cells. Both of these cells contain a diploid number of chromosomes.
  4. Mitosis occurs so that there is growth(cell division allows for growth), repair(cuts), and maintenance(replace dead cells).
  5. Mitosis consists of 4 steps. They are Prophase, Metaphase, Anaphase and Telophase. Prophase is when the chromatin coil up and conddense and shorten to form chromosomes. The spindle fibres begin to form and the nucleur membrane vanishes. Lastly, the centrioles migrate to opposite poles. In Metaphase, the spindle fibres attach to the chromsomes and allign on the equatorial plate(middle). The sister chromatids face opposite poles. In Anaphase, the centromere on the chromosome splits and the sister chromtids are pulled to opposite poles by the spindle fibres. Finally, in Telophase, the nuclear membrane forms around the chromatids and the spindle fibres disappear and the chromatids decondense to chromatin. In Cytokinesis, the cytoplasm divides and forms 2 daughter cells. Both of these cells contain a diploid number of chromosomes.
  6. Meiosis is the transfer of genetic information from generation to generation. The purpose of meiosis is for reproduction.
  7. Meiosis has two stages, Meiosis one and Meiosis two. In Meiosis one, there is interphase, Prohpase 1, Metaphase 1, Anaphase 1, Telophase 1 and Cytokinesis 1. In Interphase, the chromosomes are not condensed. The chromosomes replicate, cell growth and replication takes place and chromosomes have pairs of identical sister chromatids. In Prophase 1, the cohromosomes condnse, chromosomes pair up and find each other, the chromosmes form Homologous pairs and cross over and the nuclear membrane disappears. In Metaphase 1, the spindle fibres attach to the pairs of chromatids. The homologous pairs line up randomly in the equator of the cell and have face to face pairups(go through independent assortment, which is chromosomes randomly pairing up. In Anaphase 1, the homologous chromosomes separate to opposite poles of the cell. The spindle fibre shortens and the centromeres of the chromosome do not split. In Telophase 1, the homologous chromosomes uncoil and the spindle fibres disappear. The nuclear membrane reforms but telophase one does not occur in every cell. In Meiosis 2, there is Prophase 11, Metaphase 11, Anaphase 11,Telophase 11 and Cytokinesis 11. In Prophase 11, the chromatin condenses and form visible duplicated chromosomes. The nuclear membrane disappears and spindle fibres form between the two centrioles. The chromosome are already attached to each other and have undergone crossovers. In Metaphase 11, the spindle fibres attach to the centromere of chromosomes and the chromatids line up at the equator in a single file. In Anaphase 11, the centromeres split apart and the chromatids are pulled to opposite poles of the cell. The microtubules shorten as well. In Telophase 11, the nuclear membrane reforms and each sister chromatid has 23 chromosomes. These chromosmes unwind and become less visible.
  8. Diagrams attached.
  9. Meiosis accounts for genetic variation because in Prophase 1, crossing over occurs and in Metaphase 1, independent assortment occurs. This rearranges all the genes completely and create differences in cells and people.
  10. Mitosis has 1 cell division and contains Prophase, Metaphase, Anaphase and telophase. Meiosis has 2 cell divisions and has Prophase 1, Metaphase 1, Anaphase 1, Telophase 1, Prophase 2, Metaphase 2, Anaphase 2 and Telophase 2. Mitosis is for repair, growth and maintenance while Meiosis is for reproduction purposes. At the beginning of Mitosis, the chromosme number is diploid. At the end, it is diploid as well. In Meiosis, the beginning chromosome number is diploid. At the end, the daughter cells ends up being haploid, forming gametes.

Genetics

  1. Human karyotypes are used to show all the chromosomes in a cell. They can detect chromosomal abnormalities such as a missing chromosome. There are 22 chromosomes and a pair of sex chromosomes, ordered from largest to smallest, all in pairs and all the centromeres have to be lined up.
  2. Human Karyotypes are created by staining all 23 pairs of chromosomes with a chemical dye called Giemsa. Staining these chromosomes reveal a banding pattern that is unique to that chromosome, which allows for identification, called G-banding.Karyotypes are mostly created with blood or fetal, although any tissue can be used. These fetal cells are obtained by amniocentesis or chronic villi sampling.
  3. Some examples of disorders are Down syndrome, which is trisomy 21, Klinefelter syndrome, which is an extra x chromsome in males and gives fewer sexual traits and turner syndrome, which is a missing sex chromosome (missing Y) and reduces female traits.
  4. Examples of non-disjunction of sex shromosomes are syndromes such as Turner or Klinefelter syndrome. These syndromes typically result from chromsomes failing to separate in Meiosis 1 or 2.
  5. A mutation is an error in the DNA sequence molecule that can be caused by various factors, such as viruses.
  6. 3 types of mutations are aneuploidy, which is an extra or missing chromosome, translocation, which is chromosome pieces being mixed up and deletion, which is when a part of a chromosome has gone missing.
  7. Prenatal genetic screening occurs when mother’s would like to see if their future babies have any mutations or defects. This way, doctors can catch these problems early and try to heal them.
  8. Chorionic villi sampling is when a doctor takes a very tiny piece of placenta from a mother’s baby in her womb and takes it to detect for mutations by placing them as a karyotype. Amniocentesis is when the doctor extracts a little amount of amniotic fluid from the mother’s womb, which has blood cells that the baby has shed, and detects mutations with karyotypes.
  9. genetic trait-a charateristic of an individual that is determined from alleles and genes, height

gene- part of chromosome that is responsible for particular trait,such as using letters AA or Aa

allele- form of a gene located on a chromsome, such as the letter A in AA

purebred- having descnded from common ancestors where all share similar traits, such as size

P generation- the parent generation, with all of the original traits, such as mother AA, dad BB

F1 generation- offspring from the cross of P generation, first filial generation, such as AB

F2 generation- offspring from cross of F1 generation, second filial generation, such as AA

Dominant Allele- where the traits are always expressed in an individual, such as brown eyes

Recessive Allele- having an allele that is present but inactive such as blue eyes

Phenotype- appearance of a trait in an organism, such as the colour white

Genotype- appearance of a letter to represent the trait, such as W to represent colour white

Homozygous genotype- having 2 alleles for a trait that are the same, like AA or aa

Heterozygous genotype- having 2 letters that are different, such as Aa

Hybrid genotype- an organism heterozygous for a trait, such as Bb

Monohybrid cross- a cross of 2 heterozygous individuals, such as AaxAa

Dihybrid cross- two traits crossing together, such as colour and size together

  1. Mendel’s experiment was that he used all pea plants to create species and that when the pea plants did not change drastically, they were objecting a law. He discovered how our life works and how our traits are determined by our parents.
  2. The Principle of dominance is when individuals contrasting traits are crossed and the offspring will express only the dominant traits.
  3. The Law of segregation is the fact that heredity traits are determined by pairs of alleles form each parent. This ensures that everyone in this world is different and that we will still be able to look similar to our parents.
  4. The Law of independent assortment is that the inheritance of one trait does not affect the inheritance of another. This means that there will be different traits throughtout the body and that everyone will again, be different.
  5. To draw a punnett square, you need a tic tac toe board where u can write the 2 alleles on the sides of the table, and the various combinations are the traits.

 

  1. A test cross is a cross for an unknown genotype with a homozygous recessive individual, which determines the unknown genotypes.

17 and 18. Practice genotype problems.

19.   Incomplete dominance is when neither of the alleles controlling a trait are dominant, this create blending, such as how red flowers and white flowers sometimes blends into pink flowers. RR or R’R’ are examples of alleles that show incomplete dominance.

20.   Co-dominance is when both alleles controlling a trait are dominant. Both alleles are equally expressed and there is no blending but both phenotypes are expressed, such as a checkered feathered rooster originating from one black and one white rooster. CwCr shows the various types of one colour and how both of them are dominant, such as CwCw

21. The ABO blood typing is used for detecting what type of blood someone has. Mutiple alleles occur when there are 3 alleles and when an individual only inherits 2 of them. Some traits use more then a single pair of alleles to describe traits.

22.   A pedigree is a diagram that shows the inheritance of a single trait carried on from many generations of family members. Circle is female, square is male, half shaded means that the genotype is carried(a carrier), fully shaded means affected, and empty means that it contains normal traits. Pedigrees are used to determine the inheritance of a certain trait for your children.

24. We can determine our sex by looking at our family history and the types of diseases that we have.

25.   Thomas Morgan first stated that genetics have to be linked with our sex. He discovered that all of the white eyed flies he produced were male. This means that recessive genes will stay on the X chromosome. This means that because males only have 1 X chromosome, if there is a recessive gene on it, there will be no dominant gene to mask over it. So, most sex linked diseaeses are on males. Females have 2 X chromsomes, which can be masked with domminant traits. We can determine through people’s traits if they are male or female, based on their family history.