NMAT Review Biochem, Genetics and Central Dogma

8/19/2019 NMAT Review Biochem, Genetics and Central Dogma

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Prepared by Joshua Evans M. Bajao

National Medical

Admission Test (NMAT)

review:

Biology

Biochemistry

Macromolecules

! Simply put, a very large molecule that is

necessary for life.

! Created by the polymerization of smaller

subunits called monomers.

! 4 Types of the most important Macromolecules

Lipids Nucleic Acids

Carbohydrates Proteins

Macromolecules: Lipids

! A group of naturally occurring non-polar

molecules that contain hydrocarbons.

! Glycerol and fatty acids are the monomers of

lipids.

fatty acid

glycerol


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Macromolecules: Lipids

! Main function of lipids include energy storage,

signaling, and structural components of the cell

memrabe (Phospholipids).

! One of the main types of nutrients.

! Monosaccharides is the monomer of

carbohydrates.

! Polysaccharides may serve as a storage for

energy and or structural components.

! Includes sugars, starch, cellulose, etc.

Macromolecules: Carbohydrates

! Three of the most common disaccharides

Macromolecules: Carbohydrates

! Are large biomolecules that perform a vast array of

functions within the organism.

! Composed of one or more chains of amino acid

residues, the monomer for proteins.! The structure of an amino acid

consist of one carbon with

a carboxylic acid and an

amine group

Macromolecules: Proteins


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Macromolecules: Proteins

! Are Macromolecules composed by nucleotides.

! Nucleotides consist of a nitrogenous bases

(Adenine, Thymine, Guanine, Cytosine), a five-

carbon sugar backbone

(deoxyribose for DNA,

ribose for RNA), and a

phosphate group.

Macromolecules: Nucleic acids

CELLS Cell

! Cell is the smallest, most basic structural,

functional, and biological unit of life.

! Every organism is compose of one

(unicellular organims) or more (multicellular

organism) cell.

! It is the smallest unit of life capable of

replicating/reproducing itself independently.


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Cell Theory

! The cell is the most basic unit of life.

! All living organisms are composed of one or

more cells.

! All cells arise from pre-existing, living cells,

Matthias Schleiden and Theodore Schwann

Two types of Cells

Prokaryote Eukaryote

The main difference is that eukaryotic cell

have membrane bound organelles.

Prokaryote Anatomy Eukaryote Anatomy


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Summary:Difference between Eukaryote and Prokaryote


Size ~0 .2-2µm ~ 10-100µm

Location of genomic material

(DNA)

Nucleoid region Membrane bound nucleus

DNA Single, Circular, lackhistones

More than one, linear, withhistones (protein)

Membrane bound organelles Absent Present

RNA/protein synthesis RNA and proteins:

Cytoplasm

RNA: Nucleus (nucleolus)

Protein: Cytoplasm (free

ribosome/RER)

:

:

:

:

Summary:Difference between Eukaryote and Prokaryote


Motility Rotating Flagella (some) Undulating Flagella, Cilia

(microtubule arranged in a

9+2 manner), and orPseudopodia

Flagella Some (made of flagellin) some (made of microtubule)

Cilia Absent Some (made of microtubule)

Fimbrae and Pili Some Absent

Cell Wall Most, made of peptidoglycan Most, cellulose for plants,

chitin for fungi

-

Cell Cycle Mitosis


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Mitosis Meiosis I

Meiosis II Meiosis II: detailed


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Meiosis II: detailed

Genetics

Genetics

! Is the study of genes, heredity and genetic

variations among species.

! Gregor Johann Mendel, a scientist and an

Augustinian friar, is said to be

the father of modern genetics

due to his studies regarding the

pea plants.

Genetic terms

Gene – a stretch of DNA that determines a certain trait.

ex: Eye Color, Skin color

Allele – a specific variation of a gene.

ex: Blue eyes, green eyes, black skin, white skin

Dominant alleles – are alleles that show their effect even if the

individual has only one copy of the said allele.

Recessive alleles – are alleles that show their effect only if the

individual has two copies of the said allele.


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Genetic terms

Homozygous – a genetic condition where an individual inherits

the same alleles for a particular gene from both parents.

ex: AA, TT, yy, gg

Heterozygous – a genetic condition where an individual

inherits two different alleles of a particular gene from

both parents.

ex: Aa, Tt, Yy, Gg

Genotype – the organism’s genetic makeup

Phenotype – the organism’s observable characteristic or trait

Mendelian Inheritance (Laws)

Law Definition

Law of Segregation During gamete formation, the allele of each gene

segregate from each other so that each gametes

carries only one copy of the said gene

Law of Independent

Assortment

Genes for different trait segregate independently

from each other during gamete formation

Law of Dominance Some alleles are dominant while other are

recessive. An organism with atleast one dominant

allele will display the phenotype of the sa id allele

Mendelian Inheritance Mendelian Inheritance

If a pure bred yellow seeded pea plant was

crossed with another pea plant with a green

seeds:

a)

What is the genotypic ratio of the F2generation?

b) What is the phenotypic ration of the F2

generation


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Mendelian Inheritance

YY yyX

Gametes produced: Y Y X y y

Punnett square Y Y

y Yy Yy

y Yy Yy

Yy Yy Yy Yy


Yy YyX

Gametes produced: Y y X Y y

YY Yy Yy yy

Punnett square Y y

Y YY Yy

y Yy yy

a) Genotypic ratio is 1YY:2Yy:1yyb) Phenotypic ration: 3 Yellow: 1 Green


If a round yellow seeded pea plan that is

heterozygous on both traits were crossed to a pea

plant with the same genotype:

a)

What is the chance that the offspring will havea green seed that is wrinkled?

b) What is the chance that the offspring will have

a yellow seed that is wrinkled?

Yellow (Y) is dominant over green and round (R)

is dominant over wrinkled.


YyRr x YyRr

YR Yr yR yr x YR Yr yR yr

YR Yr yR yr

YR YYRR YYRr YyRR YyRr

Yr YYRr YYrr YyRr Yyrr

yR YyRR YyRr yyRR yyRr

yr YyRr Yyrr yyRr yyrr

*Bold letter signifies the round phenotype


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YyRr x YyRr

YY Yy Yy yy : RR Rr Rr rr

YY =!; Yy = 2/4; yy =!: RR = !; Rr = 2/4; rr = !

a) Green seed that is wrinkled = yyrr

yyrr = !(yy) x!(rr) = 1/16

b) Yellow seed that is wrinkled = Y_rr

Y_ = YY + Yy =! + 2/4 ="

Y_rr = "(Y_) x ! (rr) = 3/16


Two pea plants were crossed, there genotypes are

as follows: TtRRYy and ttRrYy (T= tall i s

dominant to short; R= rounded seed is dominant to

wrinkled; Y= yellow seed is dominant to green).

a) What fraction of the progeny will be tall, and

has a yellow wrinkled seed?

b) What about short with green round seed?

Non-Mendelian Inheritance

Sometimes called as Neo-mendelian, is any

pattern of inheritance that doesn’t confirm to

Mendel’s law of inheritance.

Examples of Non-Mendelian Inheritance

Incomplete dominance

Codominance

Multiple allele

Sex-linked

Incomplete dominance

A type of dominance that occur when the

phenotype of the heterozygous is distinct, or

often an intermediate, to phenotype of both

homozygous alleles.


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Codominance

A type of dominance that occur when both

alleles are expressed equally and is visible as a

phenotype.

Multiple allele

A type of non-Mendelian

inheritance pattern that

involves more than just

the typical two alleles

that usually code for a

certain phenotype in a

species.

Multiple allele

! Cross between AaBbCc x aaBbCC.

What is the chance that the offspring are

light colored?

"

Aa aa; BB Bb Bb bb; CC Cc

" Aa – !(Aa) x "(bb) x !(Cc) = 1/16

" aa – CC – !(aa) x "(bb) x !(CC) = 1/16

Cc – !(aa) x 2/4(Bb) x !(Cc) = 2/16

Light colored = 1/16 + 1/16 + 2/16 = 4/16 = "

Sex-linked gene

! These are genes, thus, also the allele, that

are found in the X chromosomes alone.

! The result is that the females will have two

copies of the sex-linked gene while maleswill only have one copy of the gene.

! Females that have a heterozygous allele of

a recessive trait in their genotype are calledCarriers.


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Sex-linked gene (example)

Red-green color blindness is a recessive

X-linked gene abnormality. Suppose a normal

female carrier (XCXc) has married a normal

male (XCY).

a) What is the Genotypic ratio of their

offspring.

b) What is the Phenotypic ratio of their

offspring.

XCXc x XCY

XCXC XCY XcXC XcY

a) 1 normal female: 1carrier female: 1

normal male: 1 color blind male

b) 2 normal female: 1 normal male: 1 color

blind male

Sex-linked gene (example)

Central Dogma

of MolecularBiology

Central Dogma of Molecular Biology

Replication process of producing two identicalDNA from one original DNA template

TranscriptionProcess of copying the DNA templateinto an RNA

TranslationTranslating the RNA code into a proteinsequence

DNA

RNA

Protein


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Replication

Enzymes Function

TopoIsomerase Relaxes the DNA from its super-coi led nature

Helicase Unwinds the DNA helix at the replication fork

Single Strand Binding(SSB) protein

Bind to ssDNA (single stranded DNA) to prevent itfrom re-annealing (binding) after DNA helicase

unwinds it

DNA primase Provides a starting point of RNA (or DNA) for DNApolymerase to begin synthesis of the new DNA strand

DNA polymerase Builds a new DNA strand by adding nucleotides in a5’ to 3’ direction. Also performs proof reading and

Replication

Replication

Always remember, both strand of DNA double

helix complements each other

Purines A = T Pyrimidines

G = C

5’ ATG GAG CCA GCA TCG GAT TAA 3’

3’ TAC CTC GGT CGT AGC CTA ATT 5’

Thus, A + G = T + C

Transcription

Note: RNA polymerase doesn’t need a primer to propagate

Only one strand is transcribed (template strand)

Need a promoter region


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Transcription Transcription

Always remember, like DNA, RNA complements thetemplate DNA, with one exemption: Thymine is

absent in RNA. Instead, Uracil (U) complements

Adenosine (A).

DNA template

5’ ATG GAG CCA GCA TCG GAT TAA 3’

3’ UAC CUC GGU CGU AGC CUA AUU 5’

RNA

Translation

! Translation occur in the ribosomes

! There are three kinds of RNAresponsible for translation

"

mRNA – (messenger RNA) RNA that istranscribed

" tRNA – (transfer RNA)RNA that holds theamino acid

" rRNA – (ribosomal RNA) One of theconstituents of ribosomes, together withvarious proteins.

Translation – coding

5’ AUG GAG CCA GCA UCG GAU UAA 3’

Met Glu Pro Ala Ser Asp stop


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Translation Translation

NMAT Review Biochem, Genetics and Central Dogma

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