MATERI GENETIKA: BIOLOGI KELAS 12 SMA

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Hello kids, how are you all? Meet

again with Kak Febri. This time we

will study biology for grade 12.

The material is genetics. But

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Okay, kids, this time we will

learn to enter the third chapter, namely

genetic material. For those in grade 12 who

have passed the second chapter, metabolism.

Hopefully you now understand

metabolism well. This time we will continue to

genetics material. This genetic material

is the beginning of the next chapters

which will study

Handendel's law, then there are apparent deviations

from the law, heredity patterns and so

on. So before that, let's

learn about genetic material first

. In this chapter we will learn

about chromosomes, genes and RNA.

So what are chromosomes, what are genes, what is DNA,

and what is the relationship between each of them

. Then we will also learn

about the process of protein synthesis.

the ingredients are DNA and RNA. Then

the process, the

process has two stages, namely

transcription and translation. Okay. So,

let's start from the first, namely

chromosomes, genes, and RNA. What is the

relationship between these three? What is the connection

between these three? The

first thing we see, right from class 11,

is that inside the cell there is something called the

cell nucleus. Inside the nucleus there are

chromosomes, yes. Well, this chromosome

consists of coils or twists of

chromatin threads which,

if we look at them, we examine them one by

one, these coils come from, eh,

DNA threads that roll up,

forming a coil here, the

coils form a coil between DNA

and histone proteins. So

these granules these granules are histone protein granules

that roll up along with the

DNA strands. Oh, I see. So the connection

is that DNA is a double strand.

Double strand. So there are two strands that

then bind together, that's why it's called a

double strand or double helix.

Double bonds of polynucleotides, yes. So there are a

lot of nucleotides. Later we will

learn what nucleotides are. Then the

DNA strands and histone proteins

coil around each other. DNA is a

double strand of polynucleotides that coil around each other

with histone proteins

to form chromatin threads. Yes,

these chromatin threads will later

condense and thicken to form what are

called chromosomes.

Then genes are carriers of traits that are

formed from sequences of DNA bases. So, for

example, the DNA will be from here to

here. Well, that's one gene. Come on,

let's see it better. Well,

chromosomes. If the chromosome is the

first part, from

here to here, it is the arm

, the chromosome arm. So later there will be those who

have one arm, there will be those who have two

arms. It depends on what it is, it depends on where it is

. What's this called?

Centrometer, yes. Then the size of the chromosome

is 12 to 50 microns. Micron or

micrometer. That means 12 to 50 * 10^-6

m, that's the length. Then the width

is 0.2 to 20 microns. 0.2 to

20 * 10^-6 m. Okay, that's the structure.

Based on their function, our chromosomes are

divided into autosomes and gonosomes.

The difference is that autosomes carry the

characteristics or properties of body cells.

If the gonosome carries characteristics or

gender. So,

there are only two types of gonosomes, namely X and Y. If x

combines with x, it becomes

female. If x combines with y it becomes

male. Yes,

every cell has autosomes and gonosomes. There are

44 autosomes, 2 gonosomes. That's for

body cells. But if the sex cells have

22 autosomes, the gonosome is 1. We will

discuss the number later, okay? Then

based on its shape

or based on the location of the centromere,

chromosomes are divided into four, namely

telocentric, which is A. Pay attention to the

E. The A is telocentric.

Why? Because the centromere is at

the end here, right? The centromere is at the end

so it only has one arm.

Then B. This B is

acrocentric.

So the centromere is almost at the end.

So there are two arms, but the

other arm is

very small, about 1/4 or 1/5 of the

other arm. Then

we see that C is submetacentric.

Submecentric is where one arm is

about half the length of the

other arm until

D. D is metacentric.

What's this person's name?

The centromere is in the exact middle

so that the two arms are the same length. These are

various types of chromosomes based on their

shape. Well, now let's see

how many chromosomes there are. Well, this

is a picture of our chromosome mapping.

We have 23 pairs of chromosomes

, number 1, number 2, 3, 4, 5, and

so on until chromosome pair

number 23 is the sex chromosome.

In men, the sex chromosomes are X

and Y. In women, the chromosome number

23 or sex chromosome is

X and X. The difference is the difference

between women and men. So,

what are the names of the 22 pairs mentioned earlier

?

Autosomes, yes. There are 22 pairs of autosomes,

one pair of gonosomes. Well, here are the

22 pairs of autosomes for girls and boys. There are

22 pairs of autosomes, all of which are the

same as the autosomes. But the

only difference is the gender. Sex chromosomes

or gonosomes. If male XY, if

female xx. Oh, I see. So, then

the number of chromosomes in our somatic cells

or body cells is 46 chromosomes

. 46 pieces or 23 pairs. Well,

we can see for ourselves here, there are

23 pairs. Each number is a pair,

a pair, a pair, a pair, a pair like that,

right? Usually written as 44. A is an

autosome plus XX if female or XY

if male or it can also be written as

22A 22 pairs of autosomes plus XX if

female or XY if male.

Then, in gamete cells, there are

only two gamete cells, just sperm and ovum

. Only two. Sperm, if not

ovum, only has 23 pieces.

Okay, so that means in our body cells the number of

chromosomes is 46 or 23 pairs,

usually called 2n or diploid.

Meanwhile, in gamete cells or sex cells,

the number of chromosomes is only 23.

Usually called haploid or

n ya. That's a different amount. Now let's

get into genes and DNA, shall we? If you

often hear what it is, what is it? A gene is a

combination of several or usually

tens to hundreds of DNA. The language of

DNA nucleotides combines to form a single

trait or a single gene. Then

the chromosomes are usually in pairs, right? As

we saw earlier here, each

chromosome is always in pairs

in body cells. Well, so usually genes

pair up like this. Paired

with its homologous chromosome. There are

big A and small A, right? This is big A and

small A. If A is large and A is small, it

means the allele is heterozygous. But

if A is big A big or A is small A

small, it means the name is a homozygous allele. That's how it is

. So then this is a picture of

the chromosome before it divides. If you

want to learn about cell division, in the

next chapter we will learn about

cell division. When a chromosome is about to divide, it

usually duplicates

its chromatids. So the chromatids

double like this when they are going through the

division process. Well, this means that

the picture shows that the chromosomes are not

dividing.

Well, that was it. So, the relationship between

DNA and genes. DNA that lines up in tens

to hundreds will form one

trait or one gene. Then the

paired genes are called alleles.

So, genes are alleles are pairs of

genes. If it's a single gene, if it's

two alleles, then it's a gene pair. Next

we will look at the structure of DNA. Well,

you may have often seen this DNA

in animations or in films like

Spider-Man which talk about

DNA, usually like to show

this image. This is the picture. This

is a picture of DNA. DNA is two

strands

of polynucleotides that pair up,

bond, and then coil together. So later

there will be the first strand, this one.

Then this is the second strand. The

first strand and the second strand will

bind to each other. then they

twist. Well, the DNA chain is also

called the polynucleotide chain.

Poly has a lot of nucleotides, right? Nucleotide.

Every single nucleotide must consist

of this. Well, this is what you

marked. This is called one nucleotide. There is

1P phosphate, yes. This round green one is

phosphate. Then the blue pentagon

is deoxyribose sugar.

DNA is deoxyribose nucleic acid. So

deoxyribose is the name of the sugar,

pentose sugar or pentagon sugar. Then

the one at the end is different, right? These are

all different languages,

these are called nitrogen bases.

Well, every living creature has special

properties because of the composition of its

nitrogen bases. Actually,

there are only four types of nitrogen bases.

First adenine, then guanine, then thymine,

then cytosine. Only four AGTs, those AGTs are

just repeated over and over again. But because we

have billions to trillions, there

is not a single creature in

this world that has exactly the same composition.

What differentiates one creature from

another is the composition of

its nitrogen bases. Even though there are only four,

the combination is definitely different. Well,

each nucleotide must have a phosphate, a

pentose sugar, and a nitrogen base.

Then each nucleotide

will pair with the nucleotide

opposite it. Here, please mark it. So

this nucleotide phosphate sugar base is

connected again or paired with

phosphate sugar, and the base that is

opposite it that binds later here

there is a bond between the nitrogen bases.

The bond uses hydrogen bonds, yes. Here it is

. Well, this is a hydrogen bond.

Bonding using hydrogen. Well,

then the bond is clear, the

pairing is definitely A with T, T

with A, C. C is cytocin, right? In

Indonesia, it becomes cytosine S with G, G

with S, always like that. If A is

definitely T, Hand is A and so on.

Between A and T there are

2 double hydrogen bonds. Between G and C there are

3 double hydrogen bonds. Yes, you can see it in the

picture. Well, that's how it is. So,

this means that you definitely

have to memorize that A and T are paired

and A and T are hydrogen pairs.

The bonds are double hydrogen.

Meanwhile, G and C or S

always have triple bonds. Well,

because DNA is composed of

nucleotides lined up in rows, it is

usually called a polynucleotide chain

. Then you also have to remember

what is included in the

purine language, what is included in the

pyrimidine language.

Okay, let's continue. We now come

to protein synthesis. Protein synthesis

requires DNA and RNA as materials.

So, first of all, you have to know

what the difference is between DNA

and RNA. Let's see, shall we?

Hey, before we get into the table, let's take a look at the

picture first. If it's RNA, RNA is

only one, a single strand or single

strength. If the DNA is double stranded

then it twists so it is called a

double helix. Then this is the one with the

bigger box, okay? So the difference is that

RNA doesn't have thymine,

instead it has U or uracil. Let's

see where it is first. Difference between DNA and

RNA. If DNA is located in the nucleus of

mitochondria and chloroplasts. So,

mitochondria and chloroplasts are two

organelles that have their own DNA.

Apart from ee apart from DNA eh apart from the

nucleus of mitochondria and chloroplasts, DNA is

no longer found anywhere else. But it's

different with RNA. Apart from the

nucleus, mitochondria and chloroplasts,

RNA also exists in the cytoplasm and

ribosomes. Why? Because later

protein synthesis occurs in the

cytoplasm and is also formed in the nucleus.

Then the RNA will exit into

the cytoplasm and then be

translated by the ribosome.

Then the structure of DNA is like

what I have often

repeated before, the chain is

double-stranded and the chain is long, right?

The chain is long if it is DNA. If Erna's

chain is short, her camel is single.

Why is the RNA chain short? Because

this RNA will later be formed in the form of

fragments only.

small fragments formed by

tracing DNA, we will see

later. Then if the DNA sugar is

according to its name, DNA DNA deoxyribose

nucleic acid deoxyribose nucleic acid.

The sugar is deoxyribose. If RNA is

ribose nucleic acid, ribose nucleic acid.

So the sugar is ribose sugar, right?

Nitrogen language. In DNA, the nitrogen language is

AgTS, adenine, guanine, thymine, and

cytosine. If RNA Agus, agus, adenine,

guanine, uracil, and cytosine. Yes, this is

the difference between RNA and DNA.

Then if the DNA levels remain constant.

Why stay? Because it carries a certain nature.

From the time we are born until we grow up,

our traits are carried by DNA which then

makes up our genes. So it won't

change, the level will stay the same, it won't

change. Meanwhile,

the RNA changes according to

the needs of protein synthesis. Because RNA

is the agent or executor of

protein synthesis, yes. The function of DNA is to carry

genetic material and also as a

copy, it also regulates the process of

protein synthesis. If RNA only

carries out protein synthesis. That's

different. Okay, kids, our material is

finished. I hope you can understand. Don't

forget to repeat it over and over again so you

understand better. Thank you to the younger

siblings who have listened. Don't

forget to always take care of your health and

stay enthusiastic about learning.

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