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Summary Life Science Grade 12 One-Page Summaries
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MATRIC LIFE SCIENCE ONE-PAGE SUMMARIES. SUMMARIES INCLUDE:
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Grade 12Life Science
one-page notes
and summaries
CONTAINS:
DNA
Protein Synthesis
Male Reproductive System
Responding To The Environment: PLANTS
Human Endocrine System
Human Response to the Environment
Nervous System - Reflex Action
The Eye
The Ear
Human Evolution
Natural Section Vs Artificial Selection
Evolution
Life Science Dictionary and Biological Terms
,DNA MEMO REPLICATION: DNA replication is the process during which .
a DNA molecule makes an exact copy (replica) of itself. .
A Only
Both A and B Give THREE reasons why this
B Only diagram represents Replication
B Only • 2 complimentary (new) strands forms
Deoxyribose
Add labels to the diagram G • Whole DNA molecule unwinds
below Hydrogen bond • Thymine present on the new
T A (complimentary strand)
Phosphate
G DNA REPLICATION
Deoxyribose
• The double helix unwinds.
G C • •Weak hydrogen bonds between nitrogenous bases break and two DNA
strands
• unzip (separate).
Nitrogen base Phosphate • Both DNA strand serves as templates
• •Free (DNA) nucleotides build a DNA strand onto each of the original two
Give TWO observable reasons why this diagram
represents a section of a DNA molecule •DNA strands by attaching to their complementary nitrogenous bases
(A to T and C to G).
• Double Stranded •
• Results in two identical DNA molecules. Each molecule consists of one
•original strand and one new strand.
• Base Pairing is observed (?)
NB!! Thymine not given… Can’t say Thymine (T) is present Significance of DNA replication
Differences between DNA and RNA DNA replication is important because it:
DNA RNA • Doubles the genetic material so it can be shared between the resulting daughter cells during
Double-stranded molecule Single-stranded molecule cell division.
Contains deoxyribose (sugar) Contains Ribose (sugar) • Results in the formation of identical daughter cells during mitosis
Contains nitrogen base Thymine (T) Contains the nitrogen base Uracil (U)
Big permanent molecule Short(small) temporary molecule Which TWO children are the biological
DNA profiling offspring of Cindy and George?
It can be described as an arrangement of black bars . Sipho and Litzwe
representing DNA fragments of the person. . Reason: Their bars are identical to half
Every person except Identical twins has her/his (50%) of the mom and half (50%) of the dad.
own unique DNA profile.
DNA profiling can be controversial because Other uses of DNA profiling
• Mistakes can occur during the procedure (in the lab) or the interpretation • Identify criminals •Identify dead bodies
• Can lead to stigmatisation if freely available (used by insurance companies) • Identify relatives •Identify genetic
(ancestry) Diseases/disorders
, Protein synthesis: The process by which proteins are made in each cell of an organism to form enzymes, hormones and new structures for cells.
Give 3 reasons why this diagram What is given: DNA, mRNA or tRNA?
DNA represents transcription Triplet / Codon or Anti Codon?
Shape: Double helix Triplet • Small portion of DNA unwinds
• One complimentary strand (mRNA) forms
• Uracil present on the complimentary strand
Template
•
• Transcription
mRNA - Portion of double helix DNA unwinds
•
- The double-stranded DNA unzips/weak
• hydrogen bonds break
Codons 1 2 3
• - to form two separate strands.
Identify the amino acid at:
• - One strand is used as a template
Describe the role of DNA in Protein synthesis: - to form mRNA
• • Codon 1: Serine
using free RNA nucleotides from the
• Provides the base code for the formation of a particular• -
protein nucleoplasm. • Codon 2: Glycine
- The mRNA is complementary to the
• Forms a smaller mRNA molecule, as the DNA is too big to DNA. • Codon 3: Threonine
move through the nucleopore, towards the ribosome
- mRNA now has the coded message for
Explain how a mutation on the DNA affects Protein protein synthesis.
-
Synthesis Amino Acid
Protein molecule
•Mutation on the DNA leads to a change in the mRNA sequence
Changed mRNA sequence leads to a change in the amino acid Three consecutive basis on the
•sequence (Different tRNA, carrying a different amino acid tRNA is known as an anti-codon
moves to changed mRNA
.
•Resulting in the formation of a different protein molecule Translation:
tRNA
Ribosome • Each tRNA carries a specific amino acid.
Name the amino acid that would form at X, if a mutation
• When the anticodon on the tRNA
caused Adenine to replace Uracil. Explain your Answer:
• matches the codon on the mRNA
(UCA changes to ACA)… The amino acid Threonine (DNA code ACA), • then tRNA brings the required amino acid to
• replaces the amino acid Serine (DNA code UCA)
X the ribosome.
Functions of tRNA
• • Amino acids become attached by peptide bonds
• May lead to the formation of a different protein molecule Picks up specific amino acids in the cytoplasm and
• Transfer the amino acids to the specific codon on the • to form the required protein.
mRNA at the ribosome (site of protein synthesis)
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