Life At Molecular, Cellular & Tissue Level

Question 1

What is DNA and what is its role?

Answer 1

Deoxyribose Nucleic Acid 
In the nucleus, forms chromosomes which make up the chromatin network 
Double helix - long chain (polymer) made up of monomers 
Adenine, guanine, cytosine, thymine 
ROLE
Carries hereditary info to form genes
Coding for protein synthesis 
Replication

Question 2

What is RNA and what is its role?

Answer 2

Ribonucleic Acid
Single strand, shorter than DNA
Uracil replaces thymine 
ROLE
Carries instructions from DNA in nucleus to ribosomes in cytoplasm- controls the synthesis of proteins from amino acids

Question 3

What is replication?

Answer 3

The process of making a new DNA molecule from existing DNA that’s identical to the original and it ensures the genetic code is passed to daughter cell during cell division.

Question 4

How does replication occur? (7)

Answer 4

1. Catalyzed DNA polymerase
2. Double helix unwinds
3. Weak H-bonds breaks - 2 strands unzip
4. Nucleotides in cytoplasm attach to matching base pair
5. 2 new strands of DNA is formed
6. Daughter molecules twist and form a double helix
7. Wind around histone (proteins) = chromosome

Question 5

Explain the process of protein synthesis (6)

Answer 5

1. TRANSCRIPTION: process where DNA makes and codes mRNA
2. mRNA is formed the same way replication takes place
3. mRNA moves through pores of nuclear membrane, into cytoplasm and towards ribosomes
4. TRANSLATION: anti-codon bases link to complementary bases of the codons
5. Genetic code made up of 3 bases (codons)
6. Codons match with anti-codons (attached to Amino Acids) and form a protein chain

Question 6

What are genetic aberrations and how do they occur?

Answer 6

• caused by mutations
  1. 1+ nucleotide damaged/lost (crossing over, replication, transcription)
  2. Breakdown of DNA by mutagens (environmental factors, mutagenic chemicals)

Question 7

What is meiosis? And what is its process?

Answer 7

• Cell division that takes place in the reproductive organs to produce gametes
  PROCESS
  1. DNA of parent cell - replicated in interphase
  2. Meiosis 1 - reduction division - 2 cells formed with half chromosomes
  3. Meiosis 2 - copying division - 2 haploid cells form and then divide again = 4 haploid cells

Question 8

What is crossing over?

Answer 8

Mutual exchange of pieces of chromosomes so that whole groups of genes are swopped between maternal & paternal chromosomes

Question 9

What is chromosomal non-disjunction?

Answer 9

Chromosomes fail to separate during meiosis

Question 10

What is aneuploidy?

Answer 10

Zygote has an extra or is missing a chromosome.

Question 11

What syndromes form from abnormal meiosis?

Answer 11

1. Klienfelters syndrome
   - boy born with an extra X chromosome
   = sparse body hair, enlarged breasts, small testes/penis, not a deep voice
2. Down syndrome
   - extra copy of chromosome 21
   = mental retardation, flattened facial features, heart defects

Question 12

What are genes?

Answer 12

Section of DNA that controls a hereditary characteristic

Question 13

What are alleles?

Answer 13

One of two or more forms of a gene

Controls different traits found in the same locus of homologous chromosomes

Question 14

What are genotypes?

Answer 14

Made of genes an organism carries on chromosomes, inherited from parents

Question 15

What are phenotypes?

Answer 15

Physical appearance

Question 16

What is homozygous?

Answer 16

Pair of alleles that are the same

Question 17

What is heterozygous?

Answer 17

Pair of alleles that are different

Question 18

What is Mendel’s law of segregation?

Answer 18

During meiosis, allele pairs separate = gametes have a single allele for each characteristic

Question 19

What is Mendel’s law of dominance?

Answer 19

Only the dominant trait will occur in phenotype

Question 20

What is Mendel’s law of independent assortment?

Answer 20

Alleles of different genes segregate randomly and independently during gamete formation