Inheritance

• What is DNA

  DNA stands for Deoxyribonucleic Acid. It is found in the nucleus of every nucleated cell.
• what is the function of DNA

  to instruct the cells to make proteins which allow the body to function
• what is the relationship between DNA, genes and chromosomes

  Genes are sections of coding DNA that determine a trait. Chromosomes are strands of compressed DNA that house many genes.
• What is the structure of a chromosone+ importance for cell division

  A chromosome is a long strand of DNA that has been compressed. It's important because it allows the DNA to be pulled apart easier during cell division. The centromere connects 2 sister chomatids. Different organisms have different amounts of chomosones. Man= 23. Pig=19
• What is the purpose of DNA replication?

  To produce 2 identical copies of a DNA molecule needed for cell division
• What is the process of DNA replication

  1. DNA molecule unwinds
  2. DNA molecule unzips (due to weak hydrogen bonds)
  3. Two seperate strands form
  4. Each side of the double helix acts as a template where free nucleotides join to each single strand
  5. Each new section is zipped up
  6. An identical copy of the original DNA has been created
• What is a homologous chromosome


  Pairs of matching chromosomes (one inherited from each parent) that are similar in length, gene position and centromere location. They carry the same sequence of genes but not necessarily the same alleles of those genes. In a karyotype they are paired and organised form largest to smallest. 23 pairs for humans.
• What is cell division?


  the proscess by which cells replicate their genetic material and divide to form new cells. Two types= mitosis and meiosis.
• What is mitosis?


  Type of cell division where one parent cell divides once to produce two daughter cells. The daughter cells are genetically identical to each other and the parent cell. They have the exact same chromosomes.
• What is the purpose of mitosis?

  • Asexual reproduction (unicellular organisms)
  • Growth
  • Repairing
  • Replacing old dead or damaged cells
• What is meiosis + purpose

  type of cell division where one diploid parent cell divides twice to produce four non-identical haploid daughter cells. Used to produce sex cells in organisms that reproduce sexually.
• What is the relationship between meiosis, gametes and fertilisation?

  Meiosis is where a diploid cell divides twice to produce four haploid gametes. Gametes are sex cells. Fertilisation is where two haploid gametes fuze together to form a diploid zygote.
• What is the structure of DNA?

  DNA molecules are shaped like a twisted ladder (double helix). Two strands of alternating sugar and phosphate molecules form the backbone or sides of the DNA molecule, Pairs of nitrogenous bases are found between the two strands, connected to each other by weak hydrogen bonds.
• What is a nucleotide

  A nucleotide is the building block of DNA that is made up of.

  1. A phosphate group
  2. A deoxyribose sugar
  3. one of four nitrogenous bases
• What is the complementary base pairing rule

  Nitrogenous bases only pair in a specific way.

  Adenine - Thymine

  Cytosine- Guanine
• Why does meiosis have 2 divisions?

  The first division creates 2 diploid cells (which both have 23 pairs of chromosomes) The second division splits these into 4 haploid cells with only 23 total chromosomes.
• How is genetic information passed onto offspring from both parents?

  meiosis occurs in both male and female cells to form haploid gametes with 23 chromosones. The union of the gamete in fertilisation results in offspring containing chromosones and genes, half from each parent.
• What is a karyotype + how is it organised?


  A karyotype is a pictorial representation of an individual's complete set of chromosomes.

  Homologous chromosomes are paried and organised from largest to smallest and are allocated a number from 1-22.

  The 23rd pair is the x and y chromosomes which determine the sex.
• Do differents species have different karyotypes?


  Different species of organisms have different amounts of chromosomes in their karyotypes.

  Eg: Man has 23 pairs, chickens have 39 Pairs.
• What's the difference between a male and female karyotype?

  Females have XX chromosomes

  Males have X and Y chromosone
• Whats the difference between autosomes and sex chromosomes (In a karyotype)

  Autosomes are the 44 chromosomes present in both males and females. They are matched into 22 pair based off of size, centromere position and gene location. The 23rd pari are the sex chromosomes. If there are XX it's a girl ad if there's XY it's a boy.
• What is inheritance?


  The process by which genetic information is passed on from parent to child.
• How does the work of Gregor Mendel contribute to the idea of inheritance?

  He came up with the 3 principles of inheritance:

  1. Inheritance is determined by genes passed onto offspring.
  2. Offspring Inherit one gene from each parent for each trait.
  3. A trait may not show up in one offspring but can still appear in the next generation (recessive genes).
• Define Allele


  Different forms of the same gene.

  Eg: Brown eyes, blue eyes
• What is a homozygous gene?

  Having two identical alleles for a gene- purebred

  Eg: aa or AA
• What is a Heterozygous Gene?


  Having two different alleles for a gene.

  Eg: Aa
• Genotype vs Phenotype

  • Genotype/ genome: The notation used to show the types of alleles present in the chromosome. (BB, Bb, bb)
  • Phenotype: The actual traits presented in an organism. (Brown eyes, blue eyes)
• Dominant trait


  A stronger trait that requires only one copy of the allele to be present for it to be expressed.

  Represented by capital letters

  Expressed in Homozygous dominant (AA) and Heterozygous (Aa) genotypes
• Recessive trait


  A weaker trait that requires two copies of the allele to be present for it to be expressed. Represented by lowercase letters.

  Expressed only in Homozygous Recessive genotypes (aa)
• How does sex-linked inheritance occur?

  In human + other mammals, biological sex is determined by a pair of sex chromosomes- xx(fe) xy (m).

  Genes that are found on the x chromosome are x linked. X linked traits are more common in males because generally they are recessive and men only have one x chromosome (if they have the recessive allele then no dominant allele is present to overcome recessive). Women have 2 x chromosomes which means that there is more chance a dominant trait will be present to overcome the recessive.
• What is the notation for sex-linked inheritance?

  X^H X^h= heterozygous female

  X^h Y = recessive male