17. Inheritance (Part 1) (Cambridge IGCSE Biology 0610 for exams in 2023, 2024 and 2025)

Summary

This IGCSE study video explores the concept of inheritance, explaining how genetic information is passed via DNA in chromosomes. It covers gene functions, alleles, and sex determination. The video also delves into protein synthesis via DNA transcription and mRNA translation. It distinguishes between haploid and diploid cells, outlines mitosis for growth and repair, and contrasts it with meiosis for gamete production, emphasizing their roles in cell division and genetic diversity.

Takeaways

• 🧬 **Inheritance Defined**: Inheritance is the process by which genetic information is passed from parents to offspring through DNA.
• 🧬 **DNA and Chromosomes**: DNA, carrying genetic information in genes, is located in the cell's chromosomes within the nucleus.
• 🧬 **Genes and Alleles**: Genes are sections of DNA that code for proteins and specific traits. Alleles are different versions of the same gene leading to trait variations.
• 🧬 **Sex Determination**: Humans have 23 pairs of chromosomes; the sex chromosomes (XX for females and XY for males) determine an individual's sex.
• 🧬 **Punnett Square**: A genetic diagram used to demonstrate inheritance, particularly sex inheritance, by showing possible outcomes of X and Y chromosome combinations.
• 🧬 **Protein Synthesis**: DNA provides instructions for making proteins, which are essential for various cell functions.
• 🧬 **Transcription and Translation**: The process of converting DNA sequences into proteins involves transcription (mRNA creation) and translation (amino acid assembly into proteins).
• 🧬 **Gene Expression**: Not all genes in a cell are expressed; cells produce only the proteins they need, switching genes on or off accordingly.
• 🧬 **Haploid and Diploid**: Haploid cells contain one set of chromosomes, while diploid cells have two sets, with humans having 23 pairs in diploid cells.
• 🧬 **Mitosis and Meiosis**: Mitosis is for growth and repair, producing genetically identical cells, while meiosis produces genetically different gametes with half the chromosome number.

Q & A

What is inheritance in the context of biology?

Inheritance is the process by which genetic information is passed from parents to offspring.

How is genetic information carried from parents to offspring?

Genetic information is carried in the form of DNA, which is located in the chromosomes of the cell.

What are chromosomes and where are they found?

Chromosomes are structures made of DNA that contain genetic information. They are found in the nucleus of a cell.

What is a gene and what does it control?

A gene is a length of DNA that codes for a protein. It contains instructions for specific traits or characteristics such as eye color or height.

What are alleles and how do they relate to traits?

Alleles are different versions of the same gene that can lead to variations in the trait that the gene controls.

How does the inheritance of sex in humans work?

Humans have 23 pairs of chromosomes, and one pair determines sex. Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX).

What determines the sex of a baby?

The sex of a baby depends on whether the sperm cell that fertilizes the egg contains an X or a Y chromosome.

What is the role of DNA in controlling cell function?

DNA controls cell function by controlling the production of proteins, including enzymes, membrane carriers, and receptors for neurotransmitters.

How is a protein made according to the script?

Proteins are made through a process involving transcription and translation. The gene is transcribed into mRNA, which is then translated into a protein by ribosomes.

What is the difference between haploid and diploid cells?

A haploid cell contains a single set of chromosomes, while a diploid cell contains two sets of chromosomes.

What is mitosis and what is its role in growth and repair?

Mitosis is a type of nuclear division that produces genetically identical cells. It plays a role in growth by increasing the size of organisms through cell production and in repair by promoting healing of damaged tissues.

How does meiosis differ from mitosis?

Meiosis is a reduction division that halves the chromosome number from diploid to haploid, resulting in genetically different cells. It is involved in the production of gametes. Unlike mitosis, which produces two identical daughter cells, meiosis produces four genetically different haploid cells.

Outlines

00:00

🧬 Inheritance and DNA Basics

The paragraph introduces the concept of inheritance, explaining how genetic information is passed from parents to offspring through DNA located in cell chromosomes. It details that genes, which are sections of DNA, code for proteins and determine specific traits like eye color or height. Each gene has different versions called alleles, which can lead to variations in traits. The paragraph also covers sex inheritance in humans, explaining the role of sex chromosomes (X and Y) in determining an individual's sex. It concludes with an introduction to Punnett Squares, a genetic diagram used to demonstrate inheritance.

05:03

🧬 Protein Synthesis and Cell Function

This paragraph delves into how DNA provides instructions for protein synthesis, which is crucial for various cell functions. It outlines the process of transcription, where the gene coding for a protein is used to make an mRNA copy in the nucleus. The mRNA then moves to the cytoplasm, where ribosomes use it to assemble amino acids into proteins in a process called translation. The paragraph also discusses how cells express only the genes needed for their specific functions, switching genes on or off as required. It introduces the concepts of haploid and diploid cells, explaining the difference between them and their roles in cell division.

10:04

🧬 Cell Division: Mitosis and Meiosis

The final paragraph discusses two types of cell division: mitosis and meiosis. Mitosis is described as a nuclear division that produces genetically identical cells, important for growth, repair of damaged tissues, and asexual reproduction. It contrasts mitosis with meiosis, which is a reduction division that halves the chromosome number to produce haploid cells, essential for the formation of gametes. The paragraph highlights the differences between the two processes, such as the number of daughter cells produced and the genetic identity of these cells. It also touches on the role of stem cells and the zygote in cell division and development.

Keywords

💡Inheritance

Inheritance refers to the process by which genetic information is passed from parents to offspring. It is the central theme of the video, focusing on how traits and characteristics are genetically encoded and transmitted. The script explains inheritance through the lens of DNA and chromosomes, emphasizing how genes carry this information.

💡DNA

DNA, or deoxyribonucleic acid, is the molecule that carries genetic information. In the video, DNA is described as being located in the chromosomes within the cell nucleus, highlighting its role in storing the instructions for life. DNA sequences are what genes are made of, and they are crucial for the inheritance of traits.

💡Chromosomes

Chromosomes are structures within the cell nucleus that are made of DNA and proteins. They carry genetic information in the form of genes. The video mentions that chromosomes are the carriers of DNA, and they are central to understanding how genetic information is organized and passed down.

💡Genes

Genes are sections of DNA that contain instructions for specific traits or characteristics, such as eye color or height. The video explains that genes are coded in DNA and come in different versions called alleles, which can lead to variations in the traits they control.

💡Alleles

Alleles are different versions of the same gene, which can result in variations of a particular trait. For example, the script mentions different alleles for blood type genes that can result in A, B, AB, or O blood types. Alleles are a key concept in understanding genetic diversity and inheritance.

💡Sex Chromosomes

Sex chromosomes are the pair of chromosomes that determine the sex of an individual. The video explains that normal human cells have 23 pairs of chromosomes, and one of these pairs is the sex chromosomes. Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX).

💡Diploid

Diploid cells contain two sets of chromosomes, one from each parent, making a total of 46 chromosomes in humans. The video uses the term to contrast with haploid cells, explaining that diploidy is the normal state for human body cells, which contain two copies of each chromosome.

💡Haploid

Haploid cells contain a single set of chromosomes, which means they have one of each type of chromosome. The video explains that gametes, such as egg and sperm cells, are haploid, containing 23 chromosomes each. This is in contrast to diploid cells, which have pairs of chromosomes.

💡Proteins

Proteins are large molecules composed of amino acids and are essential for the structure, function, and regulation of the body's tissues and organs. The video explains that DNA provides instructions for making proteins, which are crucial for various cellular functions, such as enzymes, membrane carriers, and neurotransmitter receptors.

💡Transcription

Transcription is the process by which the genetic information in a gene is copied into a molecule of messenger RNA (mRNA). The video describes transcription as the first step in protein synthesis, where the DNA sequence is used to create an mRNA template.

💡Translation

Translation is the process by which the mRNA sequence is used to assemble amino acids into a protein molecule. The video explains that after transcription, mRNA moves to the cytoplasm where ribosomes use it to build proteins, with the sequence of amino acids determined by the mRNA sequence.

💡Mitosis

Mitosis is a type of cell division that results in two genetically identical daughter cells, each with the same number of chromosomes as the parent cell. The video discusses mitosis in the context of growth, repair of damaged tissues, and replacement of cells, emphasizing its role in maintaining healthy tissues and organs.

💡Meiosis

Meiosis is a type of cell division that reduces the chromosome number by half, resulting in four genetically different cells, known as gametes. The video contrasts meiosis with mitosis, highlighting that it is involved in the production of sex cells and is crucial for sexual reproduction and genetic diversity.

Highlights

Inheritance is the process by which genetic information is passed from parents to offspring.

Genetic information is carried in the form of DNA located in the cell's chromosomes.

A gene is a length of DNA that codes for a protein.

Genes come in different versions called alleles, leading to variations in traits.

Human sex is determined by the presence of X and Y chromosomes.

Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX).

The gender of a baby depends on which sperm cell fertilizes the egg.

A Punnett Square is a genetic diagram used to demonstrate inheritance.

DNA provides instructions for making proteins, which perform various functions in cells.

The sequence of bases in a gene determines the sequence of amino acids used to make a specific protein.

The process of making proteins involves transcription and translation.

Most body cells contain the same genes, but gene expression varies depending on the cell's function.

A haploid nucleus contains a single set of chromosomes, while a diploid nucleus contains two sets.

Humans have 23 pairs of chromosomes in each cell, totaling 46 chromosomes.

Mitosis is nuclear division that produces genetically identical cells.

Meiosis is a type of nuclear division that results in genetically different cells.

Meiosis is involved in the production of gametes or sex cells.

The differences between mitosis and meiosis include the number of daughter cells produced and the genetic variation.

Transcripts

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in this video you are going to learn

part 1 of chapter 17 inheritance

inheritance is the process by which

genetic information is passed from

parents to offspring

this genetic information which is passed

from parents to offspring is carried in

the form of DNA

DNA is located in the chromosomes of the

cell

so the nucleus of a cell contains

structures called chromosomes

chromosomes are made of DNA which

contains genetic information in the form

of genes

a gene is a length of DNA that codes for

a protein

genes are sections of DNA that contain

instructions for specific traits or

characteristics such as eye color or

height

each gene comes in different versions

called alleles

these different versions of the same

gene can lead to variations in the trait

that the gene controls for example there

are different alleles of the gene that

determines blood type which can result

in the a b a b or O blood types

an allele is an alternative form of a

gene

let's learn about the inheritance of sex

in humans

normal human cells have 23 pairs of

chromosomes that is 46 chromosomes

these are known as diploid cells

one of the pairs of chromosomes that is

two chromosomes out of the 46 determines

the sex or gender of an individual

these chromosomes are therefore called

the sex chromosomes

the presence of X and Y chromosomes is

what determines sex

males have One X and one Y chromosome

that is X Y

while females have two X chromosomes XX

so all female egg cells contain only an

X chromosome whereas male sperm cells

may contain an X or a y thus the gender

of the baby depends on which sperm cell

fertilizes the egg cell

if a sperm carrying the father's X

chromosome fertilizes the egg the fetus

will be female

if a sperm carrying his Y chromosome

fertilizes the egg the fetus will be

male

six inheritance can be demonstrated

through a Panet Square which is a

genetic diagram where the X and Y

chromosomes replace the usual alleles in

the boxes we will come across more of

this type of diagram later on

when an egg cell from a female is

fertilized it always has an X chromosome

however a sperm cell from a male can

have either an X or a y chromosome

if the sperm cell that fertilizes the

egg has an X chromosome the baby will be

female

but if it has a y chromosome the baby

will be male

DNA provides instructions for making

proteins in cells these proteins perform

various functions in the cell such as

acting as enzymes that catalyze chemical

reactions carrying molecules across the

cell membranes and receiving signals

from neurotransmitters

the DNA controls cell function by

controlling the production of proteins

including enzymes

membrane carriers

and receptors for neurotransmitters

the sequence of bases in a gene

determines the sequence of amino acids

used to make a specific protein

the order of letters or bases in a gene

provides instructions to ourselves on

which order to assemble the amino acids

to create a particular protein

different sequences of amino acids give

different shapes to protein molecules

so proteins play an important role in

cell function let's learn how a protein

is made

the sequence of bases in DNA is

converted into a sequence of amino acids

to form proteins

the gene which codes for the protein is

used to make an mRNA copy in the nucleus

messenger RNA or mRNA is a copy of a

gene so it's similar to a single strand

of DNA

the MRNA copies the DNA based sequences

of the gene that codes for the protein

this is called transcription

the actual Gene coding for the protein

remains in the nucleus

mRNA molecules are made in the nucleus

and moved to the cytoplasm

the MRNA passes through the ribosomes

the ribosomes uses the MRNA Strand and

assembles amino acids into the protein

molecules in the specific order based on

the base sequences this is called

translation

the specific sequence of amino acids is

determined by the sequence of bases in

the MRNA

this order of sequence is specific to

each protein made

most body cells in an organism contain

the same genes but many genes in a

particular cell are not expressed

because the cell only makes the specific

proteins it needs

the genes for all proteins exist in

every cell

however not every type of protein is

made in every cell

depending on the sales function the cell

only makes the proteins it needs

the genes which are needed are switched

on and the genes which are not needed

are Switched Off

when a gene is switched on it is

expressed

and the corresponding protein is

produced

when the protein is not needed the gene

is Switched Off

let's learn about haploid and diploid

a haploid nucleus is a nucleus

containing a single set of chromosomes

which means it has one of each type of

chromosome

a deployed nucleus is a nucleus

containing two sets of chromosomes which

means it has a pair of each type of

chromosome

all humans have 23 different chromosomes

in each cell

so in a diploid cell there is a pair of

each type of chromosome and in a human

diploid cell there are 23 pairs of

chromosomes that is a total of 46

chromosomes

the gametes that is the egg and the

sperm cells only have one copy of each

chromosome meaning they have a total of

23 chromosomes in each cell

nuclei with one set of unpaired

chromosomes are known as haploid nuclei

now let's learn about mitosis

mitosis is nuclear division giving rise

to genetically identical cells

the details of the stages of mitosis are

not required

the role of mitosis in growth is that it

helps organisms increase in size by

producing new cells the role of mitosis

in the repair of damaged tissues is that

it promotes healing

mitosis is important for the replacement

of cells it continuously replaces old

cells ensuring proper tissue and organ

function and also mitosis is important

in asexual reproduction it is involved

in the production of genetically

identical Offspring without

fertilization

the exact replication of chromosomes

occurs before mitosis

during mitosis the copies of chromosomes

separate maintaining the chromosome

number in each daughter cell

so in our body cells there are two

copies of each chromosome which makes

them diploid before the cells divide the

chromosomes make copies of themselves

this ensures that when the cell splits

into two each new cell still has two

copies of each chromosome keeping them

deployed

stem cells are unspecialized cells that

divide by mitosis to produce daughter

cells that can become specialized for

specific functions

the zygote is an example of a stem cell

it is a fertilized egg cell that has the

ability to divide by mitosis and

specialize into different cell types

during early development

next meiosis

meiosis is a type of nuclear division

also known as a reduction division in

which the chromosome number is halved

from diploid to haploid resulting in

genetically different cells

meiosis is involved in the production of

gametes or six cells

the details of the stages of meiosis are

not required

unlike mitosis where the number of

chromosomes is doubled meiosis is a

process where the number of chromosomes

is halved

so let's take a quick look at the

differences between mitosis and meiosis

in mitosis two daughter cells are

produced whereas in meiosis four

daughter cells are produced

so daughter cells are deployed in

mitosis and in meiosis daughter cells

are haploid

in mitosis genetically identical

daughter cells are produced whereas in

meiosis genetically different daughter

cells are produced

only one cell division occurs in mitosis

but in meiosis two cell divisions occur

so that concludes part 1 of chapter 17

inheritance

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