W9L2 - Human Genetics 1

Question 1

What are the phenotypes of Down’s Syndrome

Answer 1

Distinctive physical characteristics

• Sloping forehead
• Protruding tongue
• Short stubby limbs
• Slightly flattened nose
• May have congenital eye, ear, heart deficits

These are examples of phenotypes

Question 2

Define Phenotype

Answer 2

Observable properties of an organism produced by:

(a) genotype; and
(b) environmental influences

(Examples: hair colour, EF abilites, height, conditions)

Question 3

How many cells are there in a human body. And how many chromosomes are in a human cell.

Answer 3

• Human body contains 100 trillion cells.
• There is a nucleus within each human cell
• And each nucleus contains 46 chromones, arranged in 23 pairs

Question 4

How are chromosomes arranged. What is within the chromosones?

Answer 4

• 46 chromsomes arranged in 23 pairs
• (one set from mother and one set from father)
• Autosomes: 1-22
• Sex chromosome: 23
  
  • The chromosomes are filled up with tightly coiled strandes of DNA

Question 5

What are gamates

Answer 5

Sex cells - Sperm from male and ova from female

• Gamates each contain only 23 chromosomes

Question 6

What do chromosomes carry. What are chromosomes-pairs?

Answer 6

Genetic information, arranged in a linear sequence

• Each chromosome carries genes of the same type
• Chromosome-pairs match in size and functions they serve

Question 7

What are chromosomes made up of?

Answer 7

Chromosomes are made up of chromatin

• Chromatin constitutes nucleic acids (DNA and RNA) and proteins

Question 8

When are chromosomes visible?

Answer 8

Only during cell division process (meitosis and meiosis)

Question 9

What is a karyotype

Answer 9

• Description of chromosonal content in a cell, which includes
• number. of chromosomes and description of sex chromosomes
  
  • Autosomes are numbered 1 to 22
  • Sex chromosomes are either X or Y

Question 10

What happens in XY + extra 21 (Total 47)

Answer 10

Male’s down syndrome

Question 11

What happens in XX + extra 21 (Total 47)

Answer 11

Female’s Down

Question 12

What happens in 45, X

Answer 12

Turner’s Syndrome (Females only)

• Timmy turner is a female!

Question 13

What happens in 47, XXY

Answer 13

Klinefelter’s Syndrome (Males only)

Question 14

How does XXY affect development. Write down 3 ways.

Answer 14

Kleinfelter’s Syndrome

Physical development

• Lagging
• Weak muscles and reduced strength

Language Development

• Between 25-85% of XXY males have langauge difficulties

Social development

• XXY males tend to be more quiet and undemanding compared to XY males

Question 15

Define nucleotide

Answer 15

Building blocks of DNA/RNA

Base + Sugar + Phosphate Group

• Sequence of DNA is described by the order of bases (ATGC) in a 5” prime end to 3” prime end

Question 16

What is the sequence of DNA. How is it related to genes?

Answer 16

Order of bases in a 5’ to 3’ direction

DNA

• Double stranded structure that consist of 2 nucleotides held together by hydrogen bonds between the bases in opposing strands
• DNA molecules are organised into stretches of sequence called genes

Question 17

When can a gene influence development

Answer 17

It can only influence when it is turned on and expressed

i.e. it must be transribed

Question 18

What is a locus

Answer 18

Sequence of DNA on specific location in chromosome

Question 19

How is RNA related to DNA

Answer 19

RNA converts (transcribe and translate) the genetic information contained within DNA to a format used to build proteins

Question 20

How does mRNA code for each amino acid

Answer 20

Using codons: Groups of three bases of mRNA

• There are 64 possible codons but there are only 20 different amino acids (which codes for everything)

Question 21

What are proteins (in terms of genes). How many are there

Answer 21

• Proteins are the end product of gene expression
• 20 different kinds (though there are 64 possible codons)

Question 22

What are 4 main types of mutation

Answer 22

1. Base substitution
2. Deletions of DNA
3. Insertion of DNA
4. Whole/partial chromosonal abnormalities

Question 23

What are alleles. How many

Answer 23

• One of two or more variations or a gene
• About one-third of humans genes are alleles
  
  • The allele of a given gene influences same trait or characteristic, and fiferent alleles results in different characteristics

Question 24

What is the SNP

Answer 24

Variation in one base pair

Question 25

What are forms of a gene that is expressed/not expressed

Answer 25

_Dominant Allele:_ * Form of gene expressed if present _Recessive Allele:_ * Not expressed if dominant allele is present

Question 26

Are traits governeed by more than one gene? What is this called?

Answer 26

_Polygenic Inheritance_ Yes most traist are governed by more than one gene

Question 27

What is the difference between mitosis and meiosis

Answer 27

_Mitosis_ * Each daughter cell with 46 chromosomes * Cell separates the chromosomes into two identical sets, in two separate nuclei _Meiosis:_ * Each daughter cell with 23 chromosomes * The DNA is replicated, recombined, and the cell divides twice * Gamates

Question 28

What is mitosis

Answer 28

_Mitosis_ * Cells separate chromosomes in nucleus to 2 identical sets in 2 separate nucleii * 2 Daughter Cells which are genetically identical to each other and their parent cell

Question 29

What is meiosis

Answer 29

_Meiosis_ * Necessary for sexual reproduction * Produces gametes (X/Y) * DNA is replicated, recombined, and cell divides twice * Results in 4 daughter cells

Question 30

What are genetic mutations

Answer 30

* Process of change in sequence of DNA * They are the source of genetic variation and basis for natural selection * Base subsittutions * Deletions of DNA * Insertion of DNA * Whole or partial chromosonal abnormalities